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Sample records for distant femtosecond laser

  1. Femtosecond laser materials processing

    SciTech Connect

    Stuart, B. C., LLNL

    1998-06-02

    Femtosecond lasers enable materials processing of most any material with extremely high precision and negligible shock or thermal loading to the surrounding area Applications ranging from drilling teeth to cutting explosives to making high-aspect ratio cuts in metals with no heat-affected zone are made possible by this technology For material removal at reasonable rates, we developed a fully computer-controlled 15-Watt average power, 100-fs laser machining system.

  2. Femtosecond Laser Materials Processing

    SciTech Connect

    Banks, P.S.; Stuart, B.C.; Komashko, A.M.; Feit, M.D.; Rubenchik, A.M.; Perry, M.D.

    2000-03-06

    The use of femtosecond lasers allows materials processing of practically any material with extremely high precision and minimal collateral damage. Advantages over conventional laser machining (using pulses longer than a few tens of picoseconds) are realized by depositing the laser energy into the electrons of the material on a time scale short compared to the transfer time of this energy to the bulk of the material, resulting in increased ablation efficiency and negligible shock or thermal stress. The improvement in the morphology by using femtosecond pulses rather than nanosecond pulses has been studied in numerous materials from biologic materials to dielectrics to metals. During the drilling process, we have observed the onset of small channels which drill faster than the surrounding material.

  3. Advances in femtosecond laser technology

    PubMed Central

    Callou, Thais Pinheiro; Garcia, Renato; Mukai, Adriana; Giacomin, Natalia T; de Souza, Rodrigo Guimarães; Bechara, Samir J

    2016-01-01

    Femtosecond laser technology has become widely adopted by ophthalmic surgeons. The purpose of this study is to discuss applications and advantages of femtosecond lasers over traditional manual techniques, and related unique complications in cataract surgery and corneal refractive surgical procedures, including: LASIK flap creation, intracorneal ring segment implantation, presbyopic treatments, keratoplasty, astigmatic keratotomy, and intrastromal lenticule procedures. PMID:27143847

  4. Advances in femtosecond laser technology.

    PubMed

    Callou, Thais Pinheiro; Garcia, Renato; Mukai, Adriana; Giacomin, Natalia T; de Souza, Rodrigo Guimarães; Bechara, Samir J

    2016-01-01

    Femtosecond laser technology has become widely adopted by ophthalmic surgeons. The purpose of this study is to discuss applications and advantages of femtosecond lasers over traditional manual techniques, and related unique complications in cataract surgery and corneal refractive surgical procedures, including: LASIK flap creation, intracorneal ring segment implantation, presbyopic treatments, keratoplasty, astigmatic keratotomy, and intrastromal lenticule procedures. PMID:27143847

  5. Femtosecond laser cataract surgery.

    PubMed

    Nagy, Zoltan Z; McAlinden, Colm

    2015-01-01

    Femtosecond laser (FSL) cataract surgery is in its infancy but is rapidly gaining popularity due to the improved consistency and predictability for corneal incisions and anterior capsulorhexis. It enables subsequently less phacoemulsification energy and time to be employed, which has gains in terms of reduced corneal oedema. In addition, the FSL allows better circularity of the anterior capsulotomy, capsule overlap, intraocular lens (IOL) placement and centration of the IOL. These advantages have resulted in improved visual and refractive outcomes in the short term. Complication rates are low which reduce with surgeon experience. This review article focuses on the Alcon LenSx system. PMID:26605364

  6. Femtosecond laser materials processing

    SciTech Connect

    Stuart, B.C.

    1997-02-01

    The use femtosecond pulses for materials processing results in very precise cutting and drilling with high efficiency. Energy deposited in the electrons is not coupled into the bulk during the pulse, resulting in negligible shock or thermal loading to adjacent areas.

  7. Holographic vector-wave femtosecond laser processing

    NASA Astrophysics Data System (ADS)

    Hayasaki, Yoshio; Hasegawa, Satoshi

    2016-03-01

    Arbitrary and variable beam shaping of femtosecond pulses by a computer-generated hologram (CGH) displayed on a spatial light modulator (SLM) have been applied to femtosecond laser processing. The holographic femtosecond laser processing has been widely used in many applications such as two-photon polymerization, optical waveguide fabrication, fabrication of volume phase gratings in polymers, and surface nanostructuring. A vector wave that has a spatial distribution of polarization states control of femtosecond pulses gives good performances for the femtosecond laser processing. In this paper, an in- system optimization of a CGH for massively-parallel femtosecond laser processing, a dynamic control of spatial spectral dispersion to improve the focal spot shape, and the holographic vector-wave femtosecond laser processing are demonstrated.

  8. 2 micron femtosecond fiber laser

    DOEpatents

    Liu, Jian; Wan, Peng; Yang, Lihmei

    2014-07-29

    Methods and systems for generating femtosecond fiber laser pulses are disclose, including generating a signal laser pulse from a seed laser oscillator; using a first amplifier stage comprising an input and an output, wherein the signal laser pulse is coupled into the input of the first stage amplifier and the output of the first amplifier stage emits an amplified and stretched signal laser pulse; using an amplifier chain comprising an input and an output, wherein the amplified and stretched signal laser pulse from the output of the first amplifier stage is coupled into the input of the amplifier chain and the output of the amplifier chain emits a further amplified, stretched signal laser pulse. Other embodiments are described and claimed.

  9. Molecular fragmentation induced by a femtosecond laser

    NASA Astrophysics Data System (ADS)

    Kosmidis, Constantine E.; Ledingham, Kenneth W. D.; Kilic, H. S.; McCanny, T.; Singhal, Raghunandan P.; Smith, D.; Langley, Andrew J.

    1998-07-01

    The 90 femtosecond laser induced fragmentation at 375 nm for a number of different nitro-molecules is compared to that induced by a nanosecond laser at the same wavelength by means of time-of-flight mass spectrometry. The potential of femtosecond laser mass spectrometry for analytical purposes is discussed.

  10. Femtosecond lasers for machining of transparent, brittle materials: ablative vs. non-ablative femtosecond laser processing

    NASA Astrophysics Data System (ADS)

    Hendricks, F.; Matylitsky, V. V.

    2016-03-01

    This paper focuses on precision machining of transparent materials by means of ablative and non-ablative femtosecond laser processing. Ablation technology will be compared with a newly developed patent pending non-ablative femtosecond process, ClearShapeTM, using the Spectra-Physics Spirit industrial femtosecond laser.

  11. Photoemission using femtosecond laser pulses

    SciTech Connect

    Srinivasan-Rao, T.; Tsang, T.; Fischer, J.

    1991-10-01

    Successful operation of short wavelength FEL requires an electron bunch of current >100 A and normalized emittance < 1 mm-mrad. Recent experiments show that RF guns with photocathodes as the electron source may be the ideal candidate for achieving these parameters. To reduce the emittance growth due to space charge and RF dynamics effects, the gun may have to operate at high field gradient (hence at high RF frequency) and a spot size small compared to the aperture. This may necessitate the laser pulse duration to be in the subpicosecond regime to reduce the energy spread. We will present the behavior of metal photocathodes upon irradiation with femtosecond laser beams, comparison of linear and nonlinear photoemission, and scalability to high currents. Theoretical estimate of the intrinsic emittance at the photocathode in the presence of the anomalous heating of the electrons, and the tolerance on the surface roughness of the cathode material will be discussed.

  12. Femtosecond laser structuring in dielectrics

    NASA Astrophysics Data System (ADS)

    Juodkazis, Saulius

    2008-03-01

    Three-dimensional (3D) structuring of glasses, crystals, and polymers by tightly focused femtosecond laser pulses is a promising technique for microfluidic, micro-optical, photonic crystal and micro-mechanical applications [1-4]. The 3D laser micro-structuring of resists is demonstrated by direct laser writing [1] and holographic recording using phase control of interfering pulses [2]. Tightly focused laser pulses can reach dielectric breakdown irradiance without self-focusing when sub-1 ps pulses are used for laser-structuring inside dielectrics. The limiting case of microstructuring, a void recording, can be achieved [3]. The mechanism of void formation has been explained as a result of dielectric breakdown and micro-explosion. The absorption is localized within a skin depth of tens-of-nanometers in the plasma at the focus. This defines an ultimate localization of the energy delivery by a laser pulse. The absorbance reaches 0.6 in a fully ionized solid state density breakdown plasma. The high temperature and pressure buildup is large enough to generate a shock wave (strong micro-explosion). For example, a single 100 nJ laser pulse forms a void under tight focusing conditions even in the high strength sapphire (Young modulus of 400 GPa). It is considered that material fails upon compression rather than tension for which the mechanical failure threshold is by an order of magnitude smaller. This scenario of breakdown by compression is corroborated by numerical modeling of the strong explosion at our experimental conditions. Modification of materials by tightly focused femtosecond pulses opens new material processing routes for inert dielectrics [4] and can possibly be used for creation of new high-temperature and pressure phases inside the volume of irradiated samples. These regions with altered nano-structure have different chemical properties as was found in silica glass, quartz, and sapphire by wet etching of the ``shocked'' regions in aqueous solution of

  13. Synchronization of Distant Optical Clocks at the Femtosecond Level

    NASA Astrophysics Data System (ADS)

    Deschênes, Jean-Daniel; Sinclair, Laura C.; Giorgetta, Fabrizio R.; Swann, William C.; Baumann, Esther; Bergeron, Hugo; Cermak, Michael; Coddington, Ian; Newbury, Nathan R.

    2016-04-01

    The use of optical clocks or oscillators in future ultraprecise navigation, gravitational sensing, coherent arrays, and relativity experiments will require time comparison and synchronization over terrestrial or satellite free-space links. Here, we demonstrate full unambiguous synchronization of two optical time scales across a free-space link. The time deviation between synchronized time scales is below 1 fs over durations from 0.1 to 6500 s, despite atmospheric turbulence and kilometer-scale path length variations. Over 2 days, the time wander is 40 fs peak to peak. Our approach relies on the two-way reciprocity of a single-spatial-mode optical link, valid to below 225 attoseconds across a turbulent 4-km path. This femtosecond level of time-frequency transfer should enable optical networks using state-of-the-art optical clocks or oscillators.

  14. Massively parallel femtosecond laser processing.

    PubMed

    Hasegawa, Satoshi; Ito, Haruyasu; Toyoda, Haruyoshi; Hayasaki, Yoshio

    2016-08-01

    Massively parallel femtosecond laser processing with more than 1000 beams was demonstrated. Parallel beams were generated by a computer-generated hologram (CGH) displayed on a spatial light modulator (SLM). The key to this technique is to optimize the CGH in the laser processing system using a scheme called in-system optimization. It was analytically demonstrated that the number of beams is determined by the horizontal number of pixels in the SLM NSLM that is imaged at the pupil plane of an objective lens and a distance parameter pd obtained by dividing the distance between adjacent beams by the diffraction-limited beam diameter. A performance limitation of parallel laser processing in our system was estimated at NSLM of 250 and pd of 7.0. Based on these parameters, the maximum number of beams in a hexagonal close-packed structure was calculated to be 1189 by using an analytical equation. PMID:27505815

  15. Femtosecond laser ablation of enamel

    NASA Astrophysics Data System (ADS)

    Le, Quang-Tri; Bertrand, Caroline; Vilar, Rui

    2016-06-01

    The surface topographical, compositional, and structural modifications induced in human enamel by femtosecond laser ablation is studied. The laser treatments were performed using a Yb:KYW chirped-pulse-regenerative amplification laser system (560 fs and 1030 nm) and fluences up to 14 J/cm2. The ablation surfaces were studied by scanning electron microscopy, grazing incidence x-ray diffraction, and micro-Raman spectroscopy. Regardless of the fluence, the ablation surfaces were covered by a layer of resolidified material, indicating that ablation is accompanied by melting of hydroxyapatite. This layer presented pores and exploded gas bubbles, created by the release of gaseous decomposition products of hydroxyapatite (CO2 and H2O) within the liquid phase. In the specimen treated with 1-kHz repetition frequency and 14 J/cm2, thickness of the resolidified material is in the range of 300 to 900 nm. The micro-Raman analysis revealed that the resolidified material contains amorphous calcium phosphate, while grazing incidence x-ray diffraction analysis allowed detecting traces of a calcium phosphate other than hydroxyapatite, probably β-tricalcium phosphate Ca3), at the surface of this specimen. The present results show that the ablation of enamel involves melting of enamel's hydroxyapatite, but the thickness of the altered layer is very small and thermal damage of the remaining material is negligible.

  16. Progress in Cherenkov femtosecond fiber lasers

    NASA Astrophysics Data System (ADS)

    Liu, Xiaomin; Svane, Ask S.; Lægsgaard, Jesper; Tu, Haohua; Boppart, Stephen A.; Turchinovich, Dmitry

    2016-01-01

    We review the recent developments in the field of ultrafast Cherenkov fiber lasers. Two essential properties of such laser systems—broad wavelength tunability and high efficiency of Cherenkov radiation wavelength conversion are discussed. The exceptional performance of the Cherenkov fiber laser systems are highlighted—dependent on the realization scheme, the Cherenkov lasers can generate the femtosecond output tunable across the entire visible and even the UV range, and for certain designs more than 40% conversion efficiency from the pump to Cherenkov signal can be achieved. The femtosecond Cherenkov laser with all-fiber architecture is presented and discussed. Operating in the visible range, it delivers 100-200 fs wavelength-tunable pulses with multimilliwatt output power and exceptionally low noise figure an order of magnitude lower than the traditional wavelength tunable supercontinuum-based femtosecond sources. The applications for Cherenkov laser systems in practical biophotonics and biomedical applications, such as bio-imaging and microscopy, are discussed.

  17. Ultraviolet femtosecond laser ionization mass spectrometry.

    PubMed

    Imasaka, Totaro

    2008-01-01

    For this study, multiphoton ionization/mass spectrometry using an ultraviolet (UV) femtosecond laser was employed for the trace analysis of organic compounds. Some of the molecules, such as dioxins, contain several chlorine atoms and have short excited-state lifetimes due to a "heavy atom" effect. A UV femtosecond laser is, then, useful for efficient resonance excitation and subsequent ionization. A technique of multiphoton ionization using an extremely short laser pulse (e.g., <10 fs), referred to as "impulsive ionization," may have a potential for use in fragmentation-free ionization, thus providing information on molecular weight in mass spectrometry. PMID:18302290

  18. Atmospheric pressure femtosecond laser imaging mass spectrometry

    NASA Astrophysics Data System (ADS)

    Coello, Yves; Gunaratne, Tissa C.; Dantus, Marcos

    2009-02-01

    We present a novel imaging mass spectrometry technique that uses femtosecond laser pulses to directly ionize the sample. The method offers significant advantages over current techniques by eliminating the need of a laser-absorbing sample matrix, being suitable for atmospheric pressure sampling, and by providing 10μm resolution, as demonstrated here with a chemical image of vegetable cell walls.

  19. Welding of transparent polymers using femtosecond laser

    NASA Astrophysics Data System (ADS)

    Roth, Gian-Luca; Rung, Stefan; Hellmann, Ralf

    2016-02-01

    Based on nonlinear absorption, we report on laser welding of cycloolefin copolymers without any additional absorption layer employing infrared femtosecond laser. To the best of our knowledge, this is the first report of ultrashort laser welding of this material class, revealing a remarkable high processing speed of 20 mm/s in a single pass mode. Using a 1028 nm laser having a pulse duration of 220 fs at a repetition rate of 571 kHz leads to a welding seam width between 38 and 137 μm, depending on the applied laser average power. The welded joint is characterized by a maximum shear strength of 40 MPa. The experimental results are compared to those reported for femtosecond laser welding of PMMA and to those published for using a Thulium fiber laser.

  20. Femtosecond lasers for microsurgery of cornea

    NASA Astrophysics Data System (ADS)

    Vartapetov, Sergei K.; Khudyakov, D. V.; Lapshin, Konstantin E.; Obidin, Aleksei Z.; Shcherbakov, Ivan A.

    2012-03-01

    The review of femtosecond laser installations for medical applications is given and a new femtosecond ophthalmologic system for creation of a flap of corneal tissue during the LASIK operation is described. An all-fibre femtosecond laser emitting ~400-fs pulses at 1067 nm is used. The pulse repetition rate can vary from 200 kHz up to 1 MHz. The output energy of the femtosecond system does not exceed 1 μJ. A specially developed objective with small spherical and chromatic aberrations is applied to focus laser radiation to an area of an eye cornea. The size of the focusing spot does not exceed 3 μm. To process the required area, scanning by a laser beam is applied with a speed no less than 5 m s-1. At a stage of preliminary tests of the system, the Κ8 glass, organic PMMA glass and specially prepared agarose gels are used as a phantom of an eye. The femtosecond system is successfully clinically tested on a plenty of eyes of a pig and on several human eyes. The duration of the procedure of creation of a corneal flap does not exceed 20 s.

  1. Femtosecond lasers for microsurgery of cornea

    SciTech Connect

    Vartapetov, Sergei K; Khudyakov, D V; Lapshin, Konstantin E; Obidin, Aleksei Z; Shcherbakov, Ivan A

    2012-03-31

    The review of femtosecond laser installations for medical applications is given and a new femtosecond ophthalmologic system for creation of a flap of corneal tissue during the LASIK operation is described. An all-fibre femtosecond laser emitting {approx}400-fs pulses at 1067 nm is used. The pulse repetition rate can vary from 200 kHz up to 1 MHz. The output energy of the femtosecond system does not exceed 1 {mu}J. A specially developed objective with small spherical and chromatic aberrations is applied to focus laser radiation to an area of an eye cornea. The size of the focusing spot does not exceed 3 {mu}m. To process the required area, scanning by a laser beam is applied with a speed no less than 5 m s{sup -1}. At a stage of preliminary tests of the system, the {Kappa}8 glass, organic PMMA glass and specially prepared agarose gels are used as a phantom of an eye. The femtosecond system is successfully clinically tested on a plenty of eyes of a pig and on several human eyes. The duration of the procedure of creation of a corneal flap does not exceed 20 s.

  2. Femtosecond Laser Filamentation for Atmospheric Sensing

    PubMed Central

    Xu, Huai Liang; Chin, See Leang

    2011-01-01

    Powerful femtosecond laser pulses propagating in transparent materials result in the formation of self-guided structures called filaments. Such filamentation in air can be controlled to occur at a distance as far as a few kilometers, making it ideally suited for remote sensing of pollutants in the atmosphere. On the one hand, the high intensity inside the filaments can induce the fragmentation of all matters in the path of filaments, resulting in the emission of characteristic fluorescence spectra (fingerprints) from the excited fragments, which can be used for the identification of various substances including chemical and biological species. On the other hand, along with the femtosecond laser filamentation, white-light supercontinuum emission in the infrared to UV range is generated, which can be used as an ideal light source for absorption Lidar. In this paper, we present an overview of recent progress concerning remote sensing of the atmosphere using femtosecond laser filamentation. PMID:22346566

  3. Femtosecond laser sintering of copper nanoparticles

    NASA Astrophysics Data System (ADS)

    Cheng, C. W.; Chen, J. K.

    2016-04-01

    The ultrafast melting of copper nanoparticles (NPs) induced by a femtosecond laser pulse with duration of 100 fs and wavelength of 800 nm is investigated theoretically and experimentally. The Cu pattern fabricated from sintering of a Cu NP-dispersed film by the femtosecond laser at a repetition rate of 80 MHz is experimentally studied. A one-dimensional two-temperature model with temperature-dependent material properties, including the extended Drude model for dynamic optical properties and the thermophysical properties, is employed to simulate the particles ultrafast melting and re-solidification process.

  4. Nanostructures created by interfered femtosecond laser

    NASA Astrophysics Data System (ADS)

    Wang, Chao; Chang, Yun-Ching; Yao, Jimmy; Luo, Claire; Yin, Shizhuo; Ruffin, Paul; Brantley, Christina; Edwards, Eugene

    2011-10-01

    The method by applying the interfered femtosecond laser to create nanostructured copper (Cu) surface has been studied. The nanostructure created by direct laser irradiation is also realized for comparison. Results show that more uniform and finer nanostructures with sphere shape and feature size around 100 nm can be induced by the interfered laser illumination comparing with the direct laser illumination. This offers an alternative fabrication approach that the feature size and the shape of the laser induced metallic nanostructures can be highly controlled, which can extremely improve its performance in related application such as the colorized metal, catalyst, SERS substrate, and etc.

  5. Superresolved femtosecond laser nanosurgery of cells

    PubMed Central

    Pospiech, Matthias; Emons, Moritz; Kuetemeyer, Kai; Heisterkamp, Alexander; Morgner, Uwe

    2011-01-01

    We report on femtosecond nanosurgery of fluorescently labeled structures in cells with a spatially superresolved laser beam. The focal spot width is reduced using phase filtering applied with a programmable phase modulator. A comprehensive statistical analysis of the resulting cuts demonstrates an achievable average resolution enhancement of 30 %. PMID:21339872

  6. Femtosecond Laser Interaction with Energetic Materials

    SciTech Connect

    Roos, E; Benterou, J; Lee, R; Roeske, F; Stuart, B

    2002-03-25

    Femtosecond laser ablation shows promise in machining energetic materials into desired shapes with minimal thermal and mechanical effects to the remaining material. We will discuss the physical effects associated with machining energetic materials and assemblies containing energetic materials, based on experimental results. Interaction of ultra-short laser pulses with matter will produce high temperature plasma at high-pressure which results in the ablation of material. In the case of energetic material, which includes high explosives, propellants and pyrotechnics, this ablation process must be accomplished without coupling energy into the energetic material. Experiments were conducted in order to characterize and better understand the phenomena of femtosecond laser pulse ablation on a variety of explosives and propellants. Experimental data will be presented for laser fluence thresholds, machining rates, cutting depths and surface quality of the cuts.

  7. Femtosecond laser in refractive and cataract surgeries

    PubMed Central

    Liu, Han-Han; Hu, Ying; Cui, Hong-Ping

    2015-01-01

    In the past few years, 9 unique laser platforms have been brought to the market. As femtosecond (FS) laser-assisted ophthalmic surgery potentially improves patient safety and visual outcomes, this new technology indeed provides ophthalmologists a reliable new option. But this new technology also poses a range of new clinical and financial challenges for surgeons. We provide an overview of the evolution of FS laser technology for use in refractive and cataract surgeries. This review describes the available laser platforms and mainly focuses on discussing the development of ophthalmic surgery technologies. PMID:25938066

  8. Femtosecond laser microstructuring for polymeric lab-on-chips.

    PubMed

    Eaton, Shane M; De Marco, Carmela; Martinez-Vazquez, Rebeca; Ramponi, Roberta; Turri, Stefano; Cerullo, Giulio; Osellame, Roberto

    2012-08-01

    This paper provides an overview of femtosecond laser microfabrication in polymeric materials, with emphasis on lab-on-chip applications. Due to the nonlinear interaction of femtosecond laser pulses with polymers, laser-induced modifications are localized to the focal volume, enabling high resolution patterning in 3D. Femtosecond laser microfabrication offers unmatched versatility in fabricating surface microchannels and diffractive optics by means of laser ablation, buried optical waveguides and micro-optics through refractive index modification and complex 3D microstructures in photoresists by two-photon polymerization. Femtosecond laser microfabrication technology opens the door to fabricating integrated lab-on-chip devices with a single tool. PMID:22589025

  9. Femtosecond fiber laser additive manufacturing of tungsten

    NASA Astrophysics Data System (ADS)

    Bai, Shuang; Liu, Jian; Yang, Pei; Zhai, Meiyu; Huang, Huan; Yang, Lih-Mei

    2016-04-01

    Additive manufacturing (AM) is promising to produce complex shaped components, including metals and alloys, to meet requirements from different industries such as aerospace, defense and biomedicines. Current laser AM uses CW lasers and very few publications have been reported for using pulsed lasers (esp. ultrafast lasers). In this paper, additive manufacturing of Tungsten materials is investigated by using femtosecond (fs) fiber lasers. Various processing conditions are studied, which leads to desired characteristics in terms of morphology, porosity, hardness, microstructural and mechanical properties of the processed components. Fully dense Tungsten part with refined grain and increased hardness was obtained and compared with parts made with different pulse widths and CW laser. The results are evidenced that the fs laser based AM provides more dimensions to modify mechanical properties with controlled heating, rapid melting and cooling rates compared with a CW or long pulsed laser. This can greatly benefit to the make of complicated structures and materials that could not be achieved before.

  10. Micromachining soda-lime glass by femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Jia, Wei; Yu, Jian; Chai, Lu; Wang, Ching-Yue

    2015-08-01

    The physical process of forming a modified region in soda-lime glass was investigated using 1 kHz intense femtosecond laser pulses from a Ti: sapphire laser at 775 nm. Through the modifications induced by the femtosecond laser radiation using selective chemical etching techniques, we fabricated reproducible and defined microstructures and further studied their morphologies and etching properties. Moreover, a possible physical mechanism for the femtosecond laser modification in soda-lime glass was proposed.

  11. Hemifusion of cells using femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Katchinskiy, Nir; Godbout, Roseline; Goez, Helly R.; Elezzabi, Abdulhakem Y.

    2015-03-01

    Attachment of single cells via hemifusion of cellular membranes using femtosecond laser pulses is reported in this manuscript. This is a method to attach single cells using sub-10 femtosecond laser pulses, with 800 nm central wavelength delivered from a Ti:Sapphire laser is described. A fluorescent dye, Calcein AM, was used to verify that the cell's cytoplasm did not migrate from a dyed cell to a non-dyed cell, in order to ascertain that the cells did not go through cell-fusion process. An optical tweezer was used in order to assess the mechanical integrity of the attached joint membranes. Hemifusion of cellular membranes was successful without initiating full cell fusion. Attachment efficiency of 95% was achieved, while the cells' viability was preserved. The attachment was performed via the delivery of one to two trains of sub-10 femtosecond laser pulses lasting 15 milliseconds each. An ultrafast reversible destabilization of the phospholipid molecules in the cellular membranes was induced due to a laser-induced ionization process. The inner phospholipid cell membrane remained intact during the attachment procedure, and cells' cytoplasm remained isolated from the surrounding medium. The unbounded inner phospholipid molecules bonded to the nearest free phospholipid molecule, forming a joint cellular membrane at the connection point. The cellular membrane hemifusion technique can potentially provide a platform for the creation of engineered tissue and cell cultures.

  12. Femtosecond laser ablation of bovine cortical bone

    NASA Astrophysics Data System (ADS)

    Cangueiro, Liliana T.; Vilar, Rui; Botelho do Rego, Ana M.; Muralha, Vania S. F.

    2012-12-01

    We study the surface topographical, structural, and compositional modifications induced in bovine cortical bone by femtosecond laser ablation. The tests are performed in air, with a Yb:KYW chirped-pulse-regenerative amplification laser system (500 fs, 1030 nm) at fluences ranging from 0.55 to 2.24 J/cm2. The ablation process is monitored by acoustic emission measurements. The topography of the laser-treated surfaces is studied by scanning electron microscopy, and their constitution is characterized by glancing incidence x-ray diffraction, x-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and micro-Raman spectroscopy. The results show that femtosecond laser ablation allows removing bone without melting, carbonization, or cracking. The structure and composition of the remaining tissue are essentially preserved, the only constitutional changes observed being a reduction of the organic material content and a partial recrystallization of hydroxyapatite in the most superficial region of samples. The results suggest that, within this fluence range, ablation occurs by a combination of thermal and electrostatic mechanisms, with the first type of mechanism predominating at lower fluences. The associated thermal effects explain the constitutional changes observed. We show that femtosecond lasers are a promising tool for delicate orthopaedic surgeries, where small amounts of bone must be cut with negligible damage, thus minimizing surgical trauma.

  13. Femtosecond laser processing and spatial light modulator

    NASA Astrophysics Data System (ADS)

    Paivasaari, Kimmo; Silvennoinen, Martti; Kaakkunen, Jarno; Vahimaa, Pasi

    2014-03-01

    The use of the femtosecond laser enables generation of small spot sizes and ablation features. Ablation of the small features usually requires only a small amount of laser power to be delivered to the ablation spot. When using only a one beam for the ablation of the small features this process is bound to be time consuming. The spatial light modulator (SLM) together with the computer generated holograms (CGH) can be used for manipulating and shaping of the laser beam in various applications. In laser micromachining, when using laser with relatively high power, the original beam can be divided up to hundreds beams and still have the energy of the individual beam above the ablation threshold of the material. This parallel laser processing enables more efficient use of the laser power regardless of the machining task.

  14. Femtosecond laser machining of electrospun membranes

    NASA Astrophysics Data System (ADS)

    Wu, Yiquan; Vorobyev, A. Y.; Clark, Robert L.; Guo, Chunlei

    2011-01-01

    We demonstrate that a femtosecond laser can be used to machine arbitrary patterns and pattern arrays into free-standing electrospun polycaprolactone (PCL) membranes. We also examine the influence of various laser irradiation settings on the final microstructure of electrospun membranes. A beam fluence of 0.6 J/cm2 is used to ablate holes in 100 μm thick PCL membranes. The machined holes have an average diameter of 436 μm and a center-to-center spacing of 1000 μm. Based on these results, the femtosecond ablation of electrospun membranes shows great potential for fabricating a variety of functional tissue scaffolds. This technique will advance scaffold design by providing the ability to rapidly tailor surface morphology, while minimizing and controlling the deformation of the electrospun fibers.

  15. Femtosecond laser controlled wettability of solid surfaces.

    PubMed

    Yong, Jiale; Chen, Feng; Yang, Qing; Hou, Xun

    2015-12-14

    Femtosecond laser microfabrication is emerging as a hot tool for controlling the wettability of solid surfaces. This paper introduces four typical aspects of femtosecond laser induced special wettability: superhydrophobicity, underwater superoleophobicity, anisotropic wettability, and smart wettability. The static properties are characterized by the contact angle measurement, while the dynamic features are investigated by the sliding behavior of a liquid droplet. Using different materials and machining methods results in different rough microstructures, patterns, and even chemistry on the solid substrates. So, various beautiful wettabilities can be realized because wettability is mainly dependent on the surface topography and chemical composition. The distinctions of the underlying formation mechanism of these wettabilities are also described in detail. PMID:26415826

  16. Femtosecond laser-electron x-ray source

    DOEpatents

    Hartemann, Frederic V.; Baldis, Hector A.; Barty, Chris P.; Gibson, David J.; Rupp, Bernhard

    2004-04-20

    A femtosecond laser-electron X-ray source. A high-brightness relativistic electron injector produces an electron beam pulse train. A system accelerates the electron beam pulse train. The femtosecond laser-electron X-ray source includes a high intra-cavity power, mode-locked laser and an x-ray optics system.

  17. Femtosecond laser lithotripsy: feasibility and ablation mechanism

    NASA Astrophysics Data System (ADS)

    Qiu, Jinze; Teichman, Joel M. H.; Wang, Tianyi; Neev, Joseph; Glickman, Randolph D.; Chan, Kin Foong; Milner, Thomas E.

    2010-03-01

    Light emitted from a femtosecond laser is capable of plasma-induced ablation of various materials. We tested the feasibility of utilizing femtosecond-pulsed laser radiation (λ=800 nm, 140 fs, 0.9 mJ/pulse) for ablation of urinary calculi. Ablation craters were observed in human calculi of greater than 90% calcium oxalate monohydrate (COM), cystine (CYST), or magnesium ammonium phosphate hexahydrate (MAPH). Largest crater volumes were achieved on CYST stones, among the most difficult stones to fragment using Holmium:YAG (Ho:YAG) lithotripsy. Diameter of debris was characterized using optical microscopy and found to be less than 20 μm, substantially smaller than that produced by long-pulsed Ho:YAG ablation. Stone retropulsion, monitored by a high-speed camera system with a spatial resolution of 15 μm, was negligible for stones with mass as small as 0.06 g. Peak shock wave pressures were less than 2 bars, measured by a polyvinylidene fluoride (PVDF) needle hydrophone. Ablation dynamics were visualized and characterized with pump-probe imaging and fast flash photography and correlated to shock wave pressures. Because femtosecond-pulsed laser ablates urinary calculi of soft and hard compositions, with micron-sized debris, negligible stone retropulsion, and small shock wave pressures, we conclude that the approach is a promising candidate technique for lithotripsy.

  18. Blackening of magnesium alloy using femtosecond laser.

    PubMed

    Shi, Haixia; Cui, Zeqin; Wang, Wenxian; Xu, Bingshe; Gong, Dianqing; Zhang, Wei

    2015-09-01

    Magnesium alloy, a potential structural and biodegradable material, has been increasingly attracting attention. In this paper, two structures with enhanced light absorption on an AZ31B magnesium surface are fabricated by femtosecond laser texturing. Laser power and the number of laser pulses are mainly investigated for darkening effect. After irradiation, surface characteristics are analyzed by a scanning electron microscope equipped with an energy dispersive spectrometer and laser scanning confocal microscope. The darkening effect is investigated by a spectrophotometer with an integrating sphere. Microgroove and stripe structures are obtained, which are covered with homogeneous nanoprotrusions and nanoparticles. The main surface chemical composition after laser ablation is MgO. The optimal light absorption in the visible range (wavelength of 400-800 nm) reaches about 98%, which is significantly improved compared with the untreated surface. The enhanced light absorption is mainly attributed to surface structure. Femtosecond laser surface texturing technology offers potential in the application of stealth technology, airborne devices, and biomedicine. PMID:26368903

  19. Producing ORMOSIL scaffolds by femtosecond laser polymerization

    NASA Astrophysics Data System (ADS)

    Matei, A.; Zamfirescu, M.; Radu, C.; Buruiana, E. C.; Buruiana, T.; Mustaciosu, C.; Petcu, I.; Radu, M.; Dinescu, M.

    2012-07-01

    Structures with different geometries and sizes were built via direct femtosecond laser writing, starting from new organic/inorganic hybrid monomers based on hybrid methacrylate containing triethoxysilane, in addition to urethane and urea groups. Multifunctional oligomer of urethane dimethacrylate type was chosen as comonomer in polymerization experiments because dimethacrylates give rise to the formation of a polymer network, having a number of favorable properties including biocompatibility and surface nanostructuring. Free standing polymeric structures were designed and created in order to be tested in fibroblast cells culture. Investigations of the cellular adhesion, proliferation, and viability of L929 mouse fibroblasts on free-standing laser processed scaffolds were performed for different scaffold designs.

  20. Femtosecond laser crystallization of amorphous Ge

    SciTech Connect

    Salihoglu, Omer; Aydinli, Atilla; Kueruem, Ulas; Gul Yaglioglu, H.; Elmali, Ayhan

    2011-06-15

    Ultrafast crystallization of amorphous germanium (a-Ge) in ambient has been studied. Plasma enhanced chemical vapor deposition grown a-Ge was irradiated with single femtosecond laser pulses of various durations with a range of fluences from below melting to above ablation threshold. Extensive use of Raman scattering has been employed to determine post solidification features aided by scanning electron microscopy and atomic force microscopy measurements. Linewidth of the Ge optic phonon at 300 cm{sup -1} as a function of laser fluence provides a signature for the crystallization of a-Ge. Various crystallization regimes including nanostructures in the form of nanospheres have been identified.

  1. VERITAS Distant Laser Calibration and Atmospheric Monitoring

    SciTech Connect

    Hui, C. M.

    2008-12-24

    As a calibrated laser pulse propagates through the atmosphere, the intensity of the Rayleigh scattered light arriving at the VERITAS telescopes can be calculated precisely. This allows for absolute calibration of imaging atmospheric Cherenkov telescopes (IACT) to be simple and straightforward. In these proceedings, we present the comparison between laser data and simulation to estimate the light collection efficiencies of the VERITAS telescopes, and the analysis of multiple laser data sets taken in different months for atmospheric monitoring purpose.

  2. Femtosecond laser ablation of the stapes

    PubMed Central

    McCaughey, Ryan G.; Sun, Hui; Rothholtz, Vanessa S.; Juhasz, Tibor; Wong, Brian J. F.

    2014-01-01

    A femtosecond laser, normally used for LASIK eye surgery, is used to perforate cadaveric human stapes. The thermal side effects of bone ablation are measured with a thermocouple in an inner ear model and are found to be within acceptable limits for inner ear surgery. Stress and acoustic events, recorded with piezoelectric film and a microphone, respectively, are found to be negligible. Optical microscopy, scanning electron microscopy, and optical coherence tomography are used to confirm the precision of the ablation craters and lack of damage to the surrounding tissue. Ablation is compared to that from an Er:YAG laser, the current laser of choice for stapedotomy, and is found to be superior. Ultra-short-pulsed lasers offer a precise and efficient ablation of the stapes, with minimal thermal and negligible mechanical and acoustic damage. They are, therefore, ideal for stapedotomy operations. PMID:19405768

  3. Femtosecond Lasers in Ophthalmology: Surgery and Imaging

    NASA Astrophysics Data System (ADS)

    Bille, J. F.

    Ophthalmology has traditionally been the field with prevalent laser applications in medicine. The human eye is one of the most accessible human organs and its transparency for visible and near-infrared light allows optical techniques for diagnosis and treatment of almost any ocular structure. Laser vision correction (LVC) was introduced in the late 1980s. Today, the procedural ease, success rate, and lack of disturbing side-effects in laser assisted in-situ keratomileusis (LASIK) have made it the most frequently performed refractive surgical procedure (keratomileusis(greek): cornea-flap-cutting). Recently, it has been demonstrated that specific aspects of LVC can take advantage of unique light-matter interaction processes that occur with femtosecond laser pulses.

  4. Femtosecond laser ablation of the stapes

    NASA Astrophysics Data System (ADS)

    McCaughey, Ryan G.; Sun, Hui; Rothholtz, Vanessa S.; Juhasz, Tibor; Wong, Brian J. F.

    2009-03-01

    A femtosecond laser, normally used for LASIK eye surgery, is used to perforate cadaveric human stapes. The thermal side effects of bone ablation are measured with a thermocouple in an inner ear model and are found to be within acceptable limits for inner ear surgery. Stress and acoustic events, recorded with piezoelectric film and a microphone, respectively, are found to be negligible. Optical microscopy, scanning electron microscopy, and optical coherence tomography are used to confirm the precision of the ablation craters and lack of damage to the surrounding tissue. Ablation is compared to that from an Er:YAG laser, the current laser of choice for stapedotomy, and is found to be superior. Ultra-short-pulsed lasers offer a precise and efficient ablation of the stapes, with minimal thermal and negligible mechanical and acoustic damage. They are, therefore, ideal for stapedotomy operations.

  5. Femtosecond lasers in ophthalmology: clinical applications in anterior segment surgery

    NASA Astrophysics Data System (ADS)

    Juhasz, Tibor; Nagy, Zoltan; Sarayba, Melvin; Kurtz, Ronald M.

    2010-02-01

    The human eye is a favored target for laser surgery due to its accessibility via the optically transparent ocular tissue. Femtosecond lasers with confined tissue effects and minimized collateral tissue damage are primary candidates for high precision intraocular surgery. The advent of compact diode-pumped femtosecond lasers, coupled with computer controlled beam delivery devices, enabled the development of high precision femtosecond laser for ophthalmic surgery. In this article, anterior segment femtosecond laser applications currently in clinical practice and investigation are reviewed. Corneal procedures evolved first and remain dominant due to easy targeting referenced from a contact surface, such as applanation lenses placed on the eye. Adding a high precision imaging technique, such as optical coherence tomography (OCT), can enable accurate targeting of tissue beyond the cornea, such as the crystalline lens. Initial clinical results of femtosecond laser cataract surgery are discussed in detail in the latter portion part of the article.

  6. Femtosecond laser eye surgery: the first clinical experience

    NASA Astrophysics Data System (ADS)

    Juhasz, Tibor; Kurtz, Ron M.; Horvath, Christopher; Suarez, Carlos G.; Nordan, Lee; Slade, Steven

    2002-04-01

    A brief review of commercial applications of femtosecond lasers in a clinical setting with emphasis on applications to corneal surgery is presented. The first clinical results of 208 procedures conducted from June to November 2000 is reported. The results show that femtosecond lasers may be safely used as keratome for use in LASIK procedures.

  7. Nanochemical effects in femtosecond laser ablation of metals

    SciTech Connect

    Vorobyev, A. Y.; Guo, Chunlei

    2013-02-18

    We study chemical energy released from the oxidation of aluminum in multipulse femtosecond laser ablation in air and oxygen. Our study shows that the released chemical energy amounts to about 13% of the incident laser energy, and about 50% of the ablated material is oxidized. The ablated material mass per laser pulse is measured to be on the nanogram scale. Our study indicates that femtosecond laser ablation is capable of inducing nanochemical reactions since the femtosecond laser pulse can controllably produce nanoparticles, clusters, and atoms from a solid target.

  8. Noncontact microsurgery of living cell membrane using femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Ilina, I. V.; Ovchinnikov, A. V.; Sitnikov, D. S.; Chefonov, O. V.; Agranat, M. B.; Mikaelyan, A. S.

    2013-06-01

    Near-infrared femtosecond laser pulses were applied to initiate reversible permeabilization of cell membrane and inject extrinsic substances into the target cells. Successful laser-based injection of a membrane impermeable dye, as well as plasmid DNA was demonstrated.

  9. Near infrared femtosecond laser ablation of urinary calculi in water

    NASA Astrophysics Data System (ADS)

    Qiu, Jinze; Teichman, Joel M.; Kuranov, Roman V.; McElroy, Austin B.; Wang, Tianyi; Paranjape, Amit S.; Milner, Thomas E.

    2009-02-01

    Pulsed light emitted from a near infrared (λ=800nm) femtosecond laser is capable of plasma induced photodisruption of various materials. We used femtosecond laser pulses to ablate human urinary calculi. Femtosecond pulsed laser interaction with urinary calculi was investigated with various stone compositions, different incident fluences and number of applied pulses. Spectral-domain optical coherence tomography was used to image cross sections of ablation craters on the surface of urinary calculi. Our results indicate that femtosecond laser pulses can ablate various calculi compositions. Crater diameter and depth varies from tens of microns to several hundred microns when up to 1000 pulses were applied. Future studies are required to determine if pulsed near infrared femtosecond laser pulses can be applied clinically for lithotripsy of urinary calculi.

  10. Thin Film Femtosecond Laser Damage Competition

    SciTech Connect

    Stolz, C J; Ristau, D; Turowski, M; Blaschke, H

    2009-11-14

    In order to determine the current status of thin film laser resistance within the private, academic, and government sectors, a damage competition was started at the 2008 Boulder Damage Symposium. This damage competition allows a direct comparison of the current state of the art of high laser resistance coatings since they are tested using the same damage test setup and the same protocol. In 2009 a high reflector coating was selected at a wavelength of 786 nm at normal incidence at a pulse length of 180 femtoseconds. A double blind test assured sample and submitter anonymity so only a summary of the results are presented here. In addition to the laser resistance results, details of deposition processes, coating materials and layer count, and spectral results will also be shared.

  11. Optical gene transfer by femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Konig, Karsten; Riemann, Iris; Tirlapur, Uday K.

    2003-07-01

    Targeted transfection of cells is an important technique for gene therapy and related biomedical applications. We delineate how high-intensity (1012 W/cm2) near-infrared (NIR) 80 MHz nanojoule femtosecond laser pulses can create highly localised membrane perforations within a minute focal volume, enabling non-invasive direct transfection of mammalian cells with DNA. We suspended Chinese hamster ovarian (CHO), rat kangaroo kidney epithelial (PtK2) and rat fibroblast cells in 0.5 ml culture medium in a sterile miniaturized cell chamber (JenLab GmbH, Jena, Germany) containing 0.2 μg plasmid DNA vector pEGFP-N1 (4.7 kb), which codes for green fluorescent protein (GFP). The NIR laser beam was introduced into a femtosecond laser scanning microscope (JenLab GmbH, Jena, Germany; focussed on the edge of the cell membrane of a target cell for 16 ms. The integration and expression efficiency of EGFP were assessed in situ by two-photon fluorescence-lifetime imaging using time-correlated single photon counting. The unique capability to transfer foreign DNA safely and efficiently into specific cell types (including stem cells), circumventing mechanical, electrical or chemical means, will have many applications, such as targeted gene therapy and DNA vaccination.

  12. Femtosecond laser studies of ultrafast intramolecular processes

    SciTech Connect

    Hayden, C.

    1993-12-01

    The goal of this research is to better understand the detailed mechanisms of chemical reactions by observing, directly in time, the dynamics of fundamental chemical processes. In this work femtosecond laser pulses are used to initiate chemical processes and follow the progress of these processes in time. The authors are currently studying ultrafast internal conversion and subsequent intramolecular relaxation in unsaturated hydrocarbons. In addition, the authors are developing nonlinear optical techniques to prepare and monitor the time evolution of specific vibrational motions in ground electronic state molecules.

  13. Colorizing metals with femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Vorobyev, A. Y.; Guo, Chunlei

    2008-01-01

    For centuries, it had been the dream of alchemists to turn inexpensive metals into gold. Certainly, it is not enough from an alchemist's point of view to transfer only the appearance of a metal to gold. However, the possibility of rendering a certain metal to a completely different color without coating can be very interesting in its own right. In this work, we demonstrate a femtosecond laser processing technique that allows us to create a variety of colors on a metal that ultimately leads us to control its optical properties from UV to terahertz.

  14. Colorizing metals with femtosecond laser pulses

    SciTech Connect

    Vorobyev, A. Y.; Guo Chunlei

    2008-01-28

    For centuries, it had been the dream of alchemists to turn inexpensive metals into gold. Certainly, it is not enough from an alchemist's point of view to transfer only the appearance of a metal to gold. However, the possibility of rendering a certain metal to a completely different color without coating can be very interesting in its own right. In this work, we demonstrate a femtosecond laser processing technique that allows us to create a variety of colors on a metal that ultimately leads us to control its optical properties from UV to terahertz.

  15. Cornea surgery with nanojoule femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Koenig, Karsten; Wang, Bagui; Riemann, Iris; Kobow, Jens

    2005-04-01

    We report on a novel optical method for (i) flap-generation in LASIK procedures as well as (ii) for flap-free intrastromal refractive surgery based on nanojoule femtosecond laser pulses. The near infrared 200 fs pulses for multiphoton ablation have been provided by ultracompact turn-key MHz laser resonators. LASIK flaps and intracorneal cavities have been realized with high precision within living New Zealand rabbits using the system FemtoCutO (JenLab GmbH, Jena, Germany) at 800 nm laser wavelength. Using low-energy sub-2 nJ laser pulses, collateral damage due to photodisruptive and self-focusing effects was avoided. The laser ablation system consists of fast galvoscanners, focusing optics of high numerical aperture as well as a sensitive imaging system and provides also the possibility of 3D multiphoton imaging of fluorescent cellular organelles and SHG signals from collagen. Multiphoton tomography of the cornea was used to determine the exact intratissue beam position and to visualize intraocular post-laser effects. The wound healing process has been investigated up to 90 days after instrastromal laser ablation by histological analysis. Regeneration of damaged collagen structures and the migration of inflammation cells have been detected.

  16. Femtosecond laser surgery of olfactory ensheathing cells protuberance

    NASA Astrophysics Data System (ADS)

    Yang, H. F.; Zhou, M.; di, J. K.; Zhao, E. L.; Gong, A. H.

    2009-03-01

    Protuberance cutting and recoverable damage of olfactory ensheathing cells (OECs) using femto-second laser surgery are reported. The damages of OECs protuberance are induced by using femtosecond laser surgery with different laser powers and scanning velocities. Through optimizing the parameters, steady cutting of OEC protuberance is achieved. After femtosecond laser surgery with 150 μ W and 10 μm/s is conducted, we found that the cell recovers its viability, such as growth, spread, and motility 1.5 h after the damage, which prove cell’s recovery and regeneration. Current work offers a novel method for establishing cell damage model and studying on cytokinetics.

  17. Femtosecond laser cataract surgery: technology and clinical practice.

    PubMed

    Roberts, Timothy V; Lawless, Michael; Chan, Colin Ck; Jacobs, Mark; Ng, David; Bali, Shveta J; Hodge, Chris; Sutton, Gerard

    2013-03-01

    The recent introduction of femtosecond lasers to cataract surgery has generated much interest among ophthalmologists around the world. Laser cataract surgery integrates high-resolution anterior segment imaging systems with a femtosecond laser, allowing key steps of the procedure, including the primary and side-port corneal incisions, the anterior capsulotomy and fragmentation of the lens nucleus, to be performed with computer-guided laser precision. There is emerging evidence of reduced phacoemulsification time, better wound architecture and a more stable refractive result with femtosecond cataract surgery, as well as reports documenting an initial learning curve. This article will review the current state of technology and discuss our clinical experience. PMID:22788831

  18. Monolithic optofluidic ring resonator lasers created by femtosecond laser nanofabrication.

    PubMed

    Chandrahalim, Hengky; Chen, Qiushu; Said, Ali A; Dugan, Mark; Fan, Xudong

    2015-05-21

    We designed, fabricated, and characterized a monolithically integrated optofluidic ring resonator laser that is mechanically, thermally, and chemically robust. The entire device, including the ring resonator channel and sample delivery microfluidics, was created in a block of fused-silica glass using a 3-dimensional femtosecond laser writing process. The gain medium, composed of Rhodamine 6G (R6G) dissolved in quinoline, was flowed through the ring resonator. Lasing was achieved at a pump threshold of approximately 15 μJ mm(-2). Detailed analysis shows that the Q-factor of the optofluidic ring resonator is 3.3 × 10(4), which is limited by both solvent absorption and scattering loss. In particular, a Q-factor resulting from the scattering loss can be as high as 4.2 × 10(4), suggesting the feasibility of using a femtosecond laser to create high quality optical cavities. PMID:25904381

  19. Femtosecond laser polishing of optical materials

    NASA Astrophysics Data System (ADS)

    Taylor, Lauren L.; Qiao, Jun; Qiao, Jie

    2015-10-01

    Technologies including magnetorheological finishing and CNC polishing are commonly used to finish optical elements, but these methods are often expensive, generate waste through the use of fluids or abrasives, and may not be suited for specific freeform substrates due to the size and shape of finishing tools. Pulsed laser polishing has been demonstrated as a technique capable of achieving nanoscale roughness while offering waste-free fabrication, material-specific processing through direct tuning of laser radiation, and access to freeform shapes using refined beam delivery and focusing techniques. Nanosecond and microsecond pulse duration radiation has been used to perform successful melting-based polishing of a variety of different materials, but this approach leads to extensive heat accumulation resulting in subsurface damage. We have experimentally investigated the ability of femtosecond laser radiation to ablate silicon carbide and silicon. By substituting ultrafast laser radiation, polishing can be performed by direct evaporation of unwanted surface asperities with minimal heating and melting, potentially offering damage-free finishing of materials. Under unoptimized laser processing conditions, thermal effects can occur leading to material oxidation. To investigate these thermal effects, simulation of the heat accumulation mechanism in ultrafast laser ablation was performed. Simulations have been extended to investigate the optimum scanning speed and pulse energy required for processing various substrates. Modeling methodologies and simulation results will be presented.

  20. Nanodot formation induced by femtosecond laser irradiation

    SciTech Connect

    Abere, M. J.; Kang, M.; Goldman, R. S.; Yalisove, S. M.; Chen, C.; Rittman, D. R.; Phillips, J. D.; Torralva, B.

    2014-10-20

    The femtosecond laser generation of ZnSe nanoscale features on ZnSe surfaces was studied. Irradiation with multiple exposures produces 10–100 nm agglomerations of nanocrystalline ZnSe while retaining the original single crystal structure of the underlying material. The structure of these nanodots was verified using a combination of scanning transmission electron microscopy, scanning electron microscopy, and atomic force microscopy. The nanodots continue to grow hours after irradiation through a combination of bulk and surface diffusion. We suggest that in nanodot formation the result of ultrafast laser induced point defect formation is more than an order of magnitude below the ZnSe ultrafast melt threshold fluence. This unique mechanism of point defect injection will be discussed.

  1. Femtosecond fiber laser welding of dissimilar metals.

    PubMed

    Huang, Huan; Yang, Lih-Mei; Bai, Shuang; Liu, Jian

    2014-10-01

    In this paper, welding of dissimilar metals was demonstrated for the first time, to the best of our knowledge, by using a high-energy high-repetition-rate femtosecond fiber laser. Metallurgical and mechanical properties were investigated and analyzed under various processing parameters (pulse energy, repetition rate, and welding speed). Results showed that the formation of intermetallic brittle phases and welding defects could be effectively reduced. Strong welding quality with more than 210 MPa tensile strength for stainless steel-aluminum and 175 MPa tensile strength for stainless steel-magnesium has been demonstrated. A minimal heat affected zone and uniform and homogenous phase transformation in the welding region have been demonstrated. This laser-welding technique can be extended for various applications in semiconductor, automobile, aerospace, and biomedical industries. PMID:25322246

  2. Optical reprogramming with ultrashort femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Uchugonova, Aisada; Breunig, Hans G.; Batista, Ana; König, Karsten

    2015-03-01

    The use of sub-15 femtosecond laser pulses in stem cell research is explored with particular emphasis on the optical reprogramming of somatic cells. The reprogramming of somatic cells into induced pluripotent stem (iPS) cells can be evoked through the ectopic expression of defined transcription factors. Conventional approaches utilize retro/lenti-viruses to deliver genes/transcription factors as well as to facilitate the integration of transcription factors into that of the host genome. However, the use of viruses may result in insertional mutations caused by the random integration of genes and as a result, this may limit the use within clinical applications due to the risk of the formation of cancer. In this study, a new approach is demonstrated in realizing non-viral reprogramming through the use of ultrashort laser pulses, to introduce transcription factors into the cell so as to generate iPS cells.

  3. Blackening of metals using femtosecond fiber laser.

    PubMed

    Huang, Huan; Yang, Lih-Mei; Bai, Shuang; Liu, Jian

    2015-01-10

    This study presents an unprecedented high throughput processing for super-blackening and superhydrophobic/hydrophilic surface on both planar and nonplanar metals surfaces. By using a high pulse repetition rate femtosecond (fs) fiber laser, a light trapping microstructure and nanostructure is generated to absorb light from UV, visible to long-wave infrared spectral region. Different types of surface structures are produced with varying laser scanning conditions (scanning speed and pitch). The modified surface morphologies are characterized using scanning electron microscope and the blackening effect is investigated through spectral measurements. Spectral measurements show that the reflectance of the processed materials decreases sharply in a wide wavelength range and the decrease occurs at different rates for different scanning pitches and speeds. Above 98% absorption over the entire visible wavelength region and above 95% absorption over the near-infrared, middle-wave infrared and long-wave infrared regions range has been demonstrated for the surface structures, and the absorption for specific wavelengths can go above 99%. Furthermore, the processing efficiency of this fs fiber laser blackening technique is 1 order of magnitude higher than that of solid-state fs laser and 4 times higher than that of picosecond (ps) laser. Further increasing of the throughput is expected by using higher repetition and higher scanning speed. This technology offers the great potential in applications such as constructing sensitive detectors and sensors, solar energy absorber, and biomedicine. PMID:25967633

  4. Femtosecond laser enabled keratoplasty for advanced keratoconus

    PubMed Central

    Shivanna, Yathish; Nagaraja, Harsha; Kugar, Thungappa; Shetty, Rohit

    2013-01-01

    Purpose: To assess the efficacy and advantages of femtosecond laser enabled keratoplasty (FLEK) over conventional penetrating keratoplasty (PKP) in advanced keratoconus. Materials and Methods: Detailed review of literature of published randomized controlled trials of operative techniques in PKP and FLEK. Results: Fifteen studies were identified, analyzed, and compared with our outcome. FLEK was found to have better outcome in view of better and earlier stabilization uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), and better refractive outcomes with low astigmatism as compared with conventional PKP. Wound healing also was noticed to be earlier, enabling early suture removal in FLEK. Conclusions: Studies relating to FLEK have shown better results than conventional PKP, however further studies are needed to assess the safety and intraoperative complications of the procedure. PMID:23925340

  5. Femtosecond laser embedded grating micromachining of flexible PDMS plates

    NASA Astrophysics Data System (ADS)

    Cho, Sung-Hak; Chang, Won-Seok; Kim, Kwang-Ryul; Hong, Jong Wook

    2009-04-01

    We report on the femtosecond laser micromachining of photo-induced embedded diffraction grating in flexible Poly (Dimethly Siloxane) (PDMS) plates using a high-intensity femtosecond (130 fs) Ti: sapphire laser ( λp = 800 nm). The refractive index modifications with diameters ranging from 2 μm to 5 μm were photo-induced after the irradiation with peak intensities of more than 1 × 10 11 W/cm 2. The graded refractive index profile was fabricated to be a symmetric around from the center of the point at which femtosecond laser was focused. The maximum refractive index change (Δ n) was estimated to be 2 × 10 -3. By the X- Y- Z scanning of sample, the embedded diffraction grating in PDMS plate was fabricated successfully using a femtosecond laser.

  6. Modification of Carbon Nanotube Templates Using Femtosecond Laser Pulses

    NASA Astrophysics Data System (ADS)

    Chang, Won-Seok; Yoo, Byung-Hyun; Cho, Sung-Hak

    2008-08-01

    Selective modification of carbon nanotubes (CNTs) on Si substrates was performed using a femtosecond laser. The high shock wave generated by the femtosecond laser effectively removed the CNTs without damage to the Si substrate. This process has many advantages because it is performed without chemicals and is easily applied to large-area patterning. The CNTs grown by plasma-enhanced chemical vapor deposition (PECVD) have a catalyst cap at the end of the nanotube due to the tip-growth mode mechanism. For the application of an electron emission and a bio sensor, the catalyst cap is usually chemically removed, which damages the surface of the wall of the CNTs. However, precise control of the femtosecond laser power and focal position can solve this problem. Furthermore, selective cutting of carbon nanotube using a femtosecond laser does not cause any phase change in the CNTs, as usually shown in focused ion beam irradiation of the CNTs.

  7. Effective parameters for film-free femtosecond laser assisted bioprinting.

    PubMed

    Desrus, H; Chassagne, B; Moizan, F; Devillard, R; Petit, S; Kling, R; Catros, S

    2016-05-10

    Optimal conditions for femtosecond laser bioprinting setup are reported on in terms of numerical aperture and accuracy of focal spot location for different bioinks to deposit without using a metallic absorbing layer. PMID:27168307

  8. Femtosecond laser pulse induced birefringence in optically isotropic glass.

    SciTech Connect

    Vawter, Gregory Allen; Luk, Ting Shan; Guo, Junpeng; Yang, Pin; Burns, George Robert

    2003-07-01

    We used a regeneratively amplified Ti:sapphire femtosecond laser to create optical birefringence in an isotropic glass medium. Between two crossed polarizers, regions modified by the femtosecond laser show bright transmission with respect to the dark background of the isotropic glass. This observation immediately suggests that these regions possess optical birefringence. The angular dependence of transmission through the laser-modified region is consistent with that of an optically birefringent material. Laser-induced birefringence is demonstrated in different glasses, including fused silica and borosilicate glass. Experimental results indicate that the optical axes of laser-induced birefringence can be controlled by the polarization direction of the femtosecond laser. The amount of laser-induced birefringence depends on the pulse energy level and number of accumulated pulses.

  9. Combustion Diagnostics with Femtosecond Laser Radiation

    NASA Astrophysics Data System (ADS)

    Couris, S.; Kotzagianni, M.; Baskevicius, A.; Bartulevicius, T.; Sirutkaitis, V.

    2014-11-01

    In the present work, the potential of Laser Induced Breakdown Spectroscopy employing femtosecond laser pulses (fs-LIBS) for fuel-air equivalence ratio measurements in premixed methane-air and propane-air flames is presented. A Ti-Sapphire laser system (100 fs, 10 Hz, 800 nm) was used as an excitation source for the plasma creation, while a spectrometer was employed to record the plasma emission spectra. The concentration of the investigated methane-air and propane-air mixtures were expressed by the fuel mole fraction Xfuel and varied from only air - Xfuel=0 (phi=0) to only fuel - Xfuel=1 (phi=∞). The spectral characteristics of the fs-LIBS spectra are discussed, while the time and energy dependence of the main spectral features are presented. Moreover, from the analysis of fs-LIBS spectra collected at different fuel mole fractions Xfuel, it was found that the fuel variations could be very well correlated with the variation of the intensity of some spectral lines and/or their ratios. The prepared calibration curves of the fuel mole fraction Xfuel versus the atomic line total intensity ratios (Hα 656.3 nm and O (I) 777 nm) and molecular lines total intensity ratios (C2 516.5 nm and CN 388.3 nm) suggest the high potential of using fs-LIBS for the determination of the local fuel concentration and its temporal variations.

  10. Precise micromachining of materials using femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Garasz, K.; Tański, M.; Barbucha, R.; Kocik, M.

    2015-06-01

    We present the results of the experimental parametric study on efficiency, accuracy and quality of femtosecond laser micromachining of different materials. The laser micromachining process was performed with a solid-state Yb:KYW laser. The laser generates 500 fs pulses of three different wavelengths, repetition rate from 100 to 900 kHz and output power up to 50 W. This allows to perform a complex research for a wide range of parameters and materials. Laser micromachining is a process based on a laser ablation phenomenon, i.e. total evaporation of material from the target surface during laser irradiation. It is the most precise method of material removal. Applying a femtosecond laser in the process, allows the use of ultra short pulses, with a duration of 10-15 seconds, while maintaining a high laser power. The concentration of energy within a single pulse is sufficiently high to cause the detachment of particles from the irradiated target without any thermal interactions with the surrounding material. Therefore, the removal of the material occurs only in the laser focus. This allows to avoid most of the unwanted effects of the heat affected zone (HAZ). It has been established, that the quality of laser ablation process using femtosecond pulses is much higher than while using the long pulsed lasers (i.e. nanosecond). The use of femtosecond laser pulses creates therefore an attractive opportunity for high quality micromachining of many groups of materials.

  11. Laser-induced structural modifications in glass using a femtosecond laser and a CO2 laser

    NASA Astrophysics Data System (ADS)

    Tamaki, Takayuki; Nakazumi, Shinya; Nakamura, Keigo; Ono, Shunsuke

    2013-03-01

    In this paper, we present the investigation results on laser-induced structural modifications in a BK7 glass sample (OHARA, S-BSL7) by use of a femtosecond laser and a CO2 laser system. A femtosecond fiber laser system (wavelength: 1.06 μm, pulse duration: 250 fs) generates 1 MHz ultrashort laser pulses with a pulse energy up to 2 μJ, and a CO2 laser system generates CW (continuous wave) laser beam with a wavelength of 10.6 μm. Both laser beams were simultaneously irradiated on a BK7 glass substrate (30 mm × 5 mm × 0.7 mm thick). The structural modifications regions were created by translating the glass sample perpendicular to the laser axis with a distance of 1 mm and a scan speed of 0.1 mm/s. The dependence of structural modifications on the laser energy of femtosecond laser pulses and the power of CO2 laser beam were investigated. The results have demonstrated that the refractive index change region with the width of 3 μm was created with simultaneously irradiation of two laser beams although the structural modification regions, which were produced with only femtosecond laser pulses, were surface ablation. And the surface ablation regions were changed to the refractive index change regions as the energy of CO2 laser beam increase to more than 2W.

  12. Phase transitions in femtosecond laser ablation

    NASA Astrophysics Data System (ADS)

    Povarnitsyn, Mikhail E.; Khishchenko, Konstantin V.; Levashov, Pavel R.

    2009-03-01

    In this study we simulate an interaction of femtosecond laser pulses (100 fs, 800 nm, 0.1-10 J/cm 2) with metal targets of Al, Au, Cu, and Ni. For analysis of laser-induced phase transitions, melting and shock waves propagation as well as material decomposition we use an Eulerian hydrocode in conjunction with a thermodynamically complete two-temperature equation of state with stable and metastable phases. Isochoric heating, material evaporation from the free surface of the target and fast propagation of the melting and shock waves are observed. On rarefaction the liquid phase becomes metastable and its lifetime is estimated using the theory of homogeneous nucleation. Mechanical spallation of the target material at high strain rates is also possible as a result of void growth and confluence. In our simulation several ablation mechanisms are taken into account but the main issue of the material is found to originate from the metastable liquid state. It can be decomposed either into a liquid-gas mixture in the vicinity of the critical point, or into droplets at high strain rates and negative pressure. The simulation results are in agreement with available experimental findings.

  13. High power femtosecond lasers at ELI-NP

    SciTech Connect

    Dabu, Razvan

    2015-02-24

    Specifications of the high power laser system (HPLS) designed for nuclear physics experiments are presented. Configuration of the 2 × 10 PW femtosecond laser system is described. In order to reach the required laser beam parameters, advanced laser techniques are proposed for the HPLS: parametric amplification and cross-polarized wave generation for the intensity contrast improvement and spectral broadening, acousto-optic programmable filters to compensate for spectral phase dispersion, optical filters for spectrum management, combined methods for transversal laser suppression.

  14. 100 W average power femtosecond laser at 343 nm.

    PubMed

    Rothhardt, Jan; Rothhardt, Carolin; Müller, Michael; Klenke, Arno; Kienel, Marco; Demmler, Stefan; Elsmann, Tino; Rothhardt, Manfred; Limpert, Jens; Tünnermann, Andreas

    2016-04-15

    We present a femtosecond laser system delivering up to 100 W of average power at 343 nm. The laser system employs a Yb-based femtosecond fiber laser and subsequent second- and third-harmonic generation in beta barium borate (BBO) crystals. Thermal gradients within these BBO crystals are mitigated by sapphire heat spreaders directly bonded to the front and back surface of the crystals. Thus, a nearly diffraction-limited beam quality (M2 < 1.4) is achieved, despite the high thermal load to the nonlinear crystals. This laser source is expected to push many industrial and scientific applications in the future. PMID:27082370

  15. Holographic femtosecond laser manipulation for advanced material processing

    NASA Astrophysics Data System (ADS)

    Hasegawa, Satoshi; Hayasaki, Yoshio

    2016-02-01

    Parallel femtosecond laser processing using a computer-generated hologram displayed on a spatial light modulator, known as holographic femtosecond laser processing, provides the advantages of high throughput and high-energy use efficiency. Therefore, it has been widely used in many applications, including laser material processing, two-photon polymerization, two-photon microscopy, and optical manipulation of biological cells. In this paper, we review the development of holographic femtosecond laser processing over the past few years from the perspective of wavefront and polarization modulation. In particular, line-shaped and vector-wave femtosecond laser processing are addressed. These beam-shaping techniques are useful for performing large-area machining in laser cutting, peeling, and grooving of materials and for high-speed fabrication of the complex nanostructures that are applied to material-surface texturing to control tribological properties, wettability, reflectance, and retardance. Furthermore, issues related to the nonuniformity of diffraction light intensity in optical reconstruction and wavelength dispersion from a computer-generated hologram are addressed. As a result, large-scale holographic femtosecond laser processing over 1000 diffraction spots was successfully demonstrated on a glass sample.

  16. All-femtosecond laser-assisted in situ keratomileusis

    NASA Astrophysics Data System (ADS)

    Gabryte, Egle; Danieliene, Egle; Vaiceliunaite, Agne; Ruksenas, Osvaldas; Vengris, Mikas; Danielius, Romualdas

    2013-03-01

    We present a femtosecond solid-state Yb:KGW laser system capable of performing the complete laser-assisted in situ keratomileusis (LASIK) ophthalmic procedure. The fundamental infrared radiation (IR) is used to create the corneal flap, and subsequently the corneal stromal ablation is performed using the ultraviolet (UV) pulses of the fifth harmonic. The heating of cornea, ablated surface quality, and healing outcomes of the surgeries performed using the femtosecond laser system are investigated by both ex vivo and in vivo experiments and compared to the results of conventional clinical ArF excimer laser application. The results of this research indicate the feasibility of clinical application of femtosecond UV lasers for LASIK procedure.

  17. Comparative study of femtosecond and nanosecond laser ablation for propulsion applications

    NASA Astrophysics Data System (ADS)

    Ionin, A. A.; Kudryashov, S. I.; Makarov, S. V.; Seleznev, L. V.; Sinitsyn, D. V.

    2012-07-01

    Dependences of absolute vapor/plasma pressure on femtosecond and nanosecond laser intensities were obtained for graphitic materials using a non-contact broadband ultrasonic technique, and propulsion prospects of femtosecond and nanosecond laser launching approaches are discussed.

  18. Nonlinear broadband photoluminescence of graphene induced by femtosecond laser irradiation

    SciTech Connect

    Liu, Wei-Tao; Wu, S.W.; Schuck, P.J.; Salmeron, Miquel; Shen, Y.R.; Wang, F.

    2010-07-01

    Upon femtosecond laser irradiation, a bright, broadband photoluminescence is observed from graphene at frequencies well above the excitation frequency. Analyses show that it arises from radiative recombination of a broad distribution of nonequilibrium electrons and holes, generated by rapid scattering between photoexcited carriers within tens of femtoseconds after the optical excitation. Its highly unusual characteristics come from the unique electronic and structural properties of graphene.

  19. Flexible gratings fabricated in polymeric plate using femtosecond laser irradiation

    NASA Astrophysics Data System (ADS)

    Park, Jung-Kyu; Cho, Sung-Hak

    2011-05-01

    Flexible gratings embedded in poly-dimethlysiloxane (PDMS) were fabricated using femtosecond laser pulses. Photo-induced gratings in a flexible PDMS plate were directly written by a high-intensity femtosecond (130 fs) Ti: Sapphire laser ( λp=800 nm). Refractive index modifications with 4 μm diameters were photo-induced after irradiation of the femtosecond pulses with peak intensities of more than 1×10 11 W/cm 2. The graded refractive index profile was fabricated to be symmetric around the center of the focal point. The diffraction efficiency of the grating samples is measured by an He-Ne laser. The maximum value of refractive index change (Δ n) in the laser-modified regions was estimated to be approximately 3.17×10 -3.

  20. Lattice dynamics of femtosecond laser-excited antimony

    NASA Astrophysics Data System (ADS)

    Abdel-Fattah, Mahmoud Hanafy; Bugayev, Aleksey; Elsayed-Ali, Hani E.

    2016-07-01

    Ultrafast electron diffraction is used to probe the lattice dynamics of femtosecond laser-excited antimony thin film. The temporal hierarchies of the intensity and position of diffraction orders are monitored. The femtosecond laser excitation of antimony film was found to lead to initial compression after the laser pulse, which gives way to tension vibrating at new equilibrium displacement. A damped harmonic oscillator model, in which the hot electron-blast force contributes to the driving force of oscillations in lattice spacing, is used to interpret the data. The electron-phonon energy-exchange rate and the electronic Grüneisen parameter were obtained.

  1. All-fiber normal-dispersion femtosecond laser

    PubMed Central

    Kieu, K.; Wise, F. W.

    2011-01-01

    Spectral filtering of a chirped pulse can be a strong pulse-shaping mechanism in all-normal-dispersion femtosecond fiber lasers. We report an implementation of such a laser that employs only fiber-format components. The Yb-doped fiber laser includes a fiber filter, and a saturable absorber based on carbon nanotubes. The laser generates 1.5-ps, 3-nJ pulses that can be dechirped to 250 fs duration outside the cavity. PMID:18648465

  2. Optical breakdown of air triggered by femtosecond laser filaments

    NASA Astrophysics Data System (ADS)

    Polynkin, Pavel; Moloney, Jerome V.

    2011-10-01

    We report experiments on the generation of dense plasma channels in ambient air using a dual laser pulse excitation scheme. The dilute plasma produced through the filamentation of an ultraintense femtosecond laser pulse is densified via avalanche ionization driven by a co-propagating multi-Joule nanosecond pulse.

  3. Robust authentication through stochastic femtosecond laser filament induced scattering surfaces

    NASA Astrophysics Data System (ADS)

    Zhang, Haisu; Tzortzakis, Stelios

    2016-05-01

    We demonstrate a reliable authentication method by femtosecond laser filament induced scattering surfaces. The stochastic nonlinear laser fabrication nature results in unique authentication robust properties. This work provides a simple and viable solution for practical applications in product authentication, while also opens the way for incorporating such elements in transparent media and coupling those in integrated optical circuits.

  4. Femtosecond laser fabrication of monolithically integrated microfluidic sensors in glass.

    PubMed

    He, Fei; Liao, Yang; Lin, Jintian; Song, Jiangxin; Qiao, Lingling; Cheng, Ya; Sugioka, Koji

    2014-01-01

    Femtosecond lasers have revolutionized the processing of materials, since their ultrashort pulse width and extremely high peak intensity allows high-quality micro- and nanofabrication of three-dimensional (3D) structures. This unique capability opens up a new route for fabrication of microfluidic sensors for biochemical applications. The present paper presents a comprehensive review of recent advancements in femtosecond laser processing of glass for a variety of microfluidic sensor applications. These include 3D integration of micro-/nanofluidic, optofluidic, electrofluidic, surface-enhanced Raman-scattering devices, in addition to fabrication of devices for microfluidic bioassays and lab-on-fiber sensors. This paper describes the unique characteristics of femtosecond laser processing and the basic concepts involved in femtosecond laser direct writing. Advanced spatiotemporal beam shaping methods are also discussed. Typical examples of microfluidic sensors fabricated using femtosecond lasers are then highlighted, and their applications in chemical and biological sensing are described. Finally, a summary of the technology is given and the outlook for further developments in this field is considered. PMID:25330047

  5. Femtosecond Laser Fabrication of Monolithically Integrated Microfluidic Sensors in Glass

    PubMed Central

    He, Fei; Liao, Yang; Lin, Jintian; Song, Jiangxin; Qiao, Lingling; Cheng, Ya; Sugioka, Koji

    2014-01-01

    Femtosecond lasers have revolutionized the processing of materials, since their ultrashort pulse width and extremely high peak intensity allows high-quality micro- and nanofabrication of three-dimensional (3D) structures. This unique capability opens up a new route for fabrication of microfluidic sensors for biochemical applications. The present paper presents a comprehensive review of recent advancements in femtosecond laser processing of glass for a variety of microfluidic sensor applications. These include 3D integration of micro-/nanofluidic, optofluidic, electrofluidic, surface-enhanced Raman-scattering devices, in addition to fabrication of devices for microfluidic bioassays and lab-on-fiber sensors. This paper describes the unique characteristics of femtosecond laser processing and the basic concepts involved in femtosecond laser direct writing. Advanced spatiotemporal beam shaping methods are also discussed. Typical examples of microfluidic sensors fabricated using femtosecond lasers are then highlighted, and their applications in chemical and biological sensing are described. Finally, a summary of the technology is given and the outlook for further developments in this field is considered. PMID:25330047

  6. Polyatomic molecules under intense femtosecond laser irradiation.

    PubMed

    Konar, Arkaprabha; Shu, Yinan; Lozovoy, Vadim V; Jackson, James E; Levine, Benjamin G; Dantus, Marcos

    2014-12-11

    Interaction of intense laser pulses with atoms and molecules is at the forefront of atomic, molecular, and optical physics. It is the gateway to powerful new tools that include above threshold ionization, high harmonic generation, electron diffraction, molecular tomography, and attosecond pulse generation. Intense laser pulses are ideal for probing and manipulating chemical bonding. Though the behavior of atoms in strong fields has been well studied, molecules under intense fields are not as well understood and current models have failed in certain important aspects. Molecules, as opposed to atoms, present confounding possibilities of nuclear and electronic motion upon excitation. The dynamics and fragmentation patterns in response to the laser field are structure sensitive; therefore, a molecule cannot simply be treated as a "bag of atoms" during field induced ionization. In this article we present a set of experiments and theoretical calculations exploring the behavior of a large collection of aryl alkyl ketones when irradiated with intense femtosecond pulses. Specifically, we consider to what extent molecules retain their molecular identity and properties under strong laser fields. Using time-of-flight mass spectrometry in conjunction with pump-probe techniques we study the dynamical behavior of these molecules, monitoring ion yield modulation caused by intramolecular motions post ionization. The set of molecules studied is further divided into smaller sets, sorted by type and position of functional groups. The pump-probe time-delay scans show that among positional isomers the variations in relative energies, which amount to only a few hundred millielectronvolts, influence the dynamical behavior of the molecules despite their having experienced such high fields (V/Å). High level ab initio quantum chemical calculations were performed to predict molecular dynamics along with single and multiphoton resonances in the neutral and ionic states. We propose the

  7. Femtosecond Fiber Lasers Based on Dissipative Processes for Nonlinear Microscopy.

    PubMed

    Wise, Frank W

    2012-01-01

    Recent progress in the development of femtosecond-pulse fiber lasers with parameters appropriate for nonlinear microscopy is reviewed. Pulse-shaping in lasers with only normal-dispersion components is briefly described, and the performance of the resulting lasers is summarized. Fiber lasers based on the formation of dissipative solitons now offer performance competitive with that of solid-state lasers, but with the benefits of the fiber medium. Lasers based on self-similar pulse evolution in the gain section of a laser also offer a combination of short pulse duration and high pulse energy that will be attractive for applications in nonlinear bioimaging. PMID:23869163

  8. Femtosecond Fiber Lasers Based on Dissipative Processes for Nonlinear Microscopy

    PubMed Central

    Wise, Frank W.

    2012-01-01

    Recent progress in the development of femtosecond-pulse fiber lasers with parameters appropriate for nonlinear microscopy is reviewed. Pulse-shaping in lasers with only normal-dispersion components is briefly described, and the performance of the resulting lasers is summarized. Fiber lasers based on the formation of dissipative solitons now offer performance competitive with that of solid-state lasers, but with the benefits of the fiber medium. Lasers based on self-similar pulse evolution in the gain section of a laser also offer a combination of short pulse duration and high pulse energy that will be attractive for applications in nonlinear bioimaging. PMID:23869163

  9. Enhancement of peak intensity in a filament core with spatiotemporally focused femtosecond laser pulses

    SciTech Connect

    Zeng Bin; Chu Wei; Li Guihua; Zhang Haisu; Ni Jielei; Gao Hui; Liu Weiwei; Yao Jinping; Cheng Ya; Xu Zhizhan; Chin, See Leang

    2011-12-15

    We demonstrate that the peak intensity in the filament core, which is inherently limited by the intensity clamping effect during femtosecond laser filamentation, can be significantly enhanced using spatiotemporally focused femtosecond laser pulses. In addition, the filament length obtained by spatiotemporally focused femtosecond laser pulses is {approx}25 times shorter than that obtained by a conventional focusing scheme, resulting in improved high spatial resolution.

  10. Femtosecond lasers as novel tool in dental surgery

    NASA Astrophysics Data System (ADS)

    Serbin, J.; Bauer, T.; Fallnich, C.; Kasenbacher, A.; Arnold, W. H.

    2002-09-01

    There is a proven potential of femtosecond lasers for medical applications like cornea shaping [1], ear surgery or dental surgery [2]. Minimal invasive treatment of carious tissue has become an increasingly important aspect in modern dentistry. State of the art methods like grinding using turbine-driven drills or ablation by Er:YAG lasers [3] generate mechanical and thermal stress, thus generating micro cracks of several tens of microns in the enamel [4]. These cracks are starting points for new carious attacks and have to be avoided for long term success of the dental treatment. By using femtosecond lasers (1 fs=10 -15 s) for ablating dental tissue, these drawbacks can be overcome. We have demonstrated that femtosecond laser ablation offers a tool for crack-free generation of cavities in dental tissue. Furthermore, spectral analysis of the laser induced plasma has been used to indicate carious oral tissue. Our latest results on femtosecond laser dentistry will be presented, demonstrating the great potential of this kind of laser technology in medicine.

  11. Monitoring femtosecond laser microscopic photothermolysis with multimodal microscopy (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Huang, Yimei; Lui, Harvey; Zhao, Jianhua; McLean, David I.; Zeng, Haishan

    2016-02-01

    Photothermolysis induced by femtosecond (fs) lasers may be a promising modality in dermatology because of its advantages of high precision due to multiphoton absorption and deeper penetration due to the use of near infrared wavelengths. Although multiphoton absorption nonlinear effects are capable of precision targeting, the femtosecond laser photothermolysis could still have effects beyond the targeted area if a sufficiently high dose of laser light is used. Such unintended effects could be minimized by real time monitoring photothermolysis during the treatment. Targeted photothermolytic treatment of ex vivo mouse skin dermis was performed with tightly focused fs laser beams. Images of reflectance confocal microscopy (RCM), second harmonic generation (SHG), and two-photon fluorescence (TPF) of the mouse skins were obtained with integrated multimodal microscopy before, during, and after the laser treatment. The RCM, SHG, and TPF signal intensities of the treatment areas changed after high power femtosecond laser irradiation. The intensities of the RCM and SHG signals decreased when the tissue was damaged, while the intensity of the TPF signal increased when the photothermolysis was achieved. Moreover, the TPF signal was more susceptible to the degree of the photothermolysis than the RCM and SHG signals. The results suggested that multimodal microscopy is a potentially useful tool to monitor and assess the femtosecond laser treatment of the skin to achieve microscopic photothermolysis with high precision.

  12. Programmable femtosecond laser pulses in the ultraviolet

    SciTech Connect

    Hacker, M.; Feurer, T.; Sauerbrey, R.; Lucza, T.; Szabo, G.

    2001-06-01

    Using a combination of a zero-dispersion compressor and spectrally compensated sum-frequency generation, we have produced amplitude-modulated femtosecond pulses in the UV at 200 nm. {copyright} 2001 Optical Society of America

  13. Femtosecond laser three-dimensional micro- and nanofabrication

    SciTech Connect

    Sugioka, Koji; Cheng, Ya

    2014-12-15

    The rapid development of the femtosecond laser has revolutionized materials processing due to its unique characteristics of ultrashort pulse width and extremely high peak intensity. The short pulse width suppresses the formation of a heat-affected zone, which is vital for ultrahigh precision fabrication, whereas the high peak intensity allows nonlinear interactions such as multiphoton absorption and tunneling ionization to be induced in transparent materials, which provides versatility in terms of the materials that can be processed. More interestingly, irradiation with tightly focused femtosecond laser pulses inside transparent materials makes three-dimensional (3D) micro- and nanofabrication available due to efficient confinement of the nonlinear interactions within the focal volume. Additive manufacturing (stereolithography) based on multiphoton absorption (two-photon polymerization) enables the fabrication of 3D polymer micro- and nanostructures for photonic devices, micro- and nanomachines, and microfluidic devices, and has applications for biomedical and tissue engineering. Subtractive manufacturing based on internal modification and fabrication can realize the direct fabrication of 3D microfluidics, micromechanics, microelectronics, and photonic microcomponents in glass. These microcomponents can be easily integrated in a single glass microchip by a simple procedure using a femtosecond laser to realize more functional microdevices, such as optofluidics and integrated photonic microdevices. The highly localized multiphoton absorption of a tightly focused femtosecond laser in glass can also induce strong absorption only at the interface of two closely stacked glass substrates. Consequently, glass bonding can be performed based on fusion welding with femtosecond laser irradiation, which provides the potential for applications in electronics, optics, microelectromechanical systems, medical devices, microfluidic devices, and small satellites. This review paper

  14. Femtosecond laser three-dimensional micro- and nanofabrication

    NASA Astrophysics Data System (ADS)

    Sugioka, Koji; Cheng, Ya

    2014-12-01

    The rapid development of the femtosecond laser has revolutionized materials processing due to its unique characteristics of ultrashort pulse width and extremely high peak intensity. The short pulse width suppresses the formation of a heat-affected zone, which is vital for ultrahigh precision fabrication, whereas the high peak intensity allows nonlinear interactions such as multiphoton absorption and tunneling ionization to be induced in transparent materials, which provides versatility in terms of the materials that can be processed. More interestingly, irradiation with tightly focused femtosecond laser pulses inside transparent materials makes three-dimensional (3D) micro- and nanofabrication available due to efficient confinement of the nonlinear interactions within the focal volume. Additive manufacturing (stereolithography) based on multiphoton absorption (two-photon polymerization) enables the fabrication of 3D polymer micro- and nanostructures for photonic devices, micro- and nanomachines, and microfluidic devices, and has applications for biomedical and tissue engineering. Subtractive manufacturing based on internal modification and fabrication can realize the direct fabrication of 3D microfluidics, micromechanics, microelectronics, and photonic microcomponents in glass. These microcomponents can be easily integrated in a single glass microchip by a simple procedure using a femtosecond laser to realize more functional microdevices, such as optofluidics and integrated photonic microdevices. The highly localized multiphoton absorption of a tightly focused femtosecond laser in glass can also induce strong absorption only at the interface of two closely stacked glass substrates. Consequently, glass bonding can be performed based on fusion welding with femtosecond laser irradiation, which provides the potential for applications in electronics, optics, microelectromechanical systems, medical devices, microfluidic devices, and small satellites. This review paper

  15. Stabilization of femtosecond laser frequency combs with subhertz residual linewidths.

    PubMed

    Bartels, A; Oates, C W; Hollberg, L; Diddams, S A

    2004-05-15

    We demonstrate that femtosecond laser frequency combs (FLFCs) can have a subhertz linewidth across their entire emission spectra when they are phase locked to a reference laser with a similarly narrow linewidth. Correspondingly, the coherence time of the comb components relative to the reference laser can be of the order of a few seconds. Thus we are able to detect high-contrast spectral interferograms at up to 10-s integration time between two FLFCs locked to a common optical reference. PMID:15181992

  16. Femtosecond Synchronization of Laser Systems for the LCLS

    SciTech Connect

    Byrd, John; Doolittle, Lawrence; Huang, Gang; Staples, John; Wilcox, Russell; Arthur, John; Frisch, Josef; White, William; /SLAC

    2012-08-24

    The scientific potential of femtosecond x-ray pulses at linac-driven free-electron lasers such as the Linac Coherent Light Source is tremendous. Time-resolved pump-probe experiments require a measure of the relative arrival time of each x-ray pulse with respect to the experimental pump laser. An optical timing system based on stabilized fiber links has been developed for the LCLS to provide this synchronization. Preliminary results show synchronization of the installed stabilized links at the sub-20-femtosecond level. We present details of the implementation at LCLS and potential for future development.

  17. Resynchronization in neuronal network divided by femtosecond laser processing.

    PubMed

    Hosokawa, Chie; Kudoh, Suguru N; Kiyohara, Ai; Taguchi, Takahisa

    2008-05-01

    We demonstrated scission of a living neuronal network on multielectrode arrays (MEAs) using a focused femtosecond laser and evaluated the resynchronization of spontaneous electrical activity within the network. By an irradiation of femtosecond laser into hippocampal neurons cultured on a multielectrode array dish, neurites were cut at the focal point. After the irradiation, synchronization of neuronal activity within the network drastically decreased over the divided area, indicating diminished functional connections between neurons. Cross-correlation analysis revealed that spontaneous activity between the divided areas gradually resynchronized within 10 days. These findings indicate that hippocampal neurons have the potential to regenerate functional connections and to reconstruct a network by self-assembly. PMID:18418255

  18. Wavelength Effects In Femtosecond Pulsed Laser Ablation And Deposition

    SciTech Connect

    Castillejo, Marta; Nalda, Rebeca de; Oujja, Mohamed; Sanz, Mikel

    2010-10-08

    Ultrafast pulsed laser irradiation of solid materials is highly attractive for the micro-and nanostructuring of substrates and for the fabrication of nanostructured deposits. Femtosecond laser pulses promote efficient material removal with reduced heat transfer and high deposition rates of nanometer scale particles free of microscopic particulates. Most of the studies to date have been performed with light pulses centered around the peak wavelength of the Titanium:Sapphire laser, around 800 nm. Analysis of the process over a broader range of wavelengths can provide important information about the processes involved and serve as experimental tests for advanced theoretical models. We report on our current investigations on the effect that laser wavelength of femtosecond pulses has on the superficial nanostructuring induced on biopolymer substrates, and on the characteristics of nanostructured deposits grown by pulsed laser deposition from semiconductor targets.

  19. Femtosecond laser system for micromachining of the materials

    NASA Astrophysics Data System (ADS)

    Barbucha, R.; Kocik, M.; Tański, M.; Garasz, K.; Petrov, T.; Radzewicz, C.

    2015-01-01

    Femtosecond-pulse laser micromachining is based on a laser ablation phenomenon, i.e. total evaporation of material from the target surface during laser irradiation. It is the most precise method of material removal. Moreover it does not require any post processing. Removal of the material occurs only in the laser focus, since the lack of thermal interaction, neither heat affected zone (HAZ) nor debris ocur. Research results have shown that shortening the duration of the laser pulse significantly reduces HAZ, which translates into the high quality of the machined structures. It is the main argument for the use of femtosecond-pulse lasers in the precise micromachining. In this paper, a femtosecond laser system consisting of a solid-state oscillator and the ytterbium-doped pulse fiber amplifier are presented. Average beam power at 343 nm with mode-locking is 4W @25A and pulse length at the oscillator output is 500 fs. Laser micro and nano-machining has found application in different fields. It's primary use is industrial micromachining of metals, ceramics, polymers, glass, biological material for medical use in eye surgery, and photovoltaic cells.

  20. Femtosecond laser microchannels fabrication based on electrons dynamics control using temporally or spatially shaped pulses

    NASA Astrophysics Data System (ADS)

    Yan, Xueliang; Hu, Jie; Li, Xiaowei; Xia, Bo; Liu, Pengjun; Lu, Yongfeng; Jiang, Lan

    2014-11-01

    With ultrashort pulse durations and ultrahigh power densities, femtosecond laser presents unique advantages of high precision and high quality fabrication of microchannels in transparent materials. In our study, by shaping femtosecond laser pulse energy distribution in temporal or spatial domains, localized transient electrons dynamics and the subsequent processes, such as phase changes, can be controlled, leading to the dramatic increases in the capability of femtosecond laser microchannels fabrication. The temporally shaped femtosecond laser pulse trains can significantly enhance the material removal rate in both water-assisted femtosecond laser drilling and femtosecond laser irradiation followed by chemical etching. Besides, high-aspect-ratio and small-diameter microchannels are drilled by spatially shaped femtosecond laser pulses.

  1. Femtosecond laser-induced electronic plasma at metal surface

    SciTech Connect

    Chen Zhaoyang; Mao, Samuel S.

    2008-08-04

    We develop a theoretical analysis to model plasma initiation at the early stage of femtosecond laser irradiation of metal surfaces. The calculation reveals that there is a threshold intensity for the formation of a microscale electronic plasma at the laser-irradidated metal surface. As the full width at half maximum of a laser pulse increases from 15 to 200 fs, the plasma formation threshold decreases by merely about 20%. The dependence of the threshold intensity on laser pulse width can be attributed to laser-induced surface electron emission, in particular due to the effect of photoelectric effect.

  2. Ultraviolet femtosecond and nanosecond laser ablation of silicon: Ablation efficiency and laser-induced plasma expansion

    SciTech Connect

    Zeng, Xianzhong; Mao, Xianglei; Greif, Ralph; Russo, Richard E.

    2004-03-23

    Femtosecond laser ablation of silicon in air was studied and compared with nanosecond laser ablation at ultraviolet wavelength (266 nm). Laser ablation efficiency was studied by measuring crater depth as a function of pulse number. For the same number of laser pulses, the fs-ablated crater was about two times deeper than the ns-crater. The temperature and electron number density of the pulsed laser-induced plasma were determined from spectroscopic measurements. The electron number density and temperature of fs-pulse plasmas decreased faster than ns-pulse plasmas due to different energy deposition mechanisms. Images of the laser-induced plasma were obtained with femtosecond time-resolved laser shadowgraph imaging. Plasma expansion in both the perpendicular and the lateral directions to the laser beam were compared for femtosecond and nanosecond laser ablation.

  3. Development of femtosecond optical frequency comb laser tracker

    NASA Astrophysics Data System (ADS)

    Yang, Ju-qing; Zhou, Wei-hu; Dong, Deng-feng; Zhang, Zi-li; Lao, Da-bao; Ji, Rong-yi; Wang, Da-yong

    2016-01-01

    A new type femtosecond laser tracker is one high precision measurement instrument with urgent need in science research region and industrial manufacture field. This paper focuses on the operational principle and the structure development of the femtosecond laser tracer, and the method of error compensation as well. The system modules were studied and constructed. The femtosecond frequency comb module was firstly analyzed and developed. The femtosecond laser frequency comb performed perfectly high precise distance measurement for laser tracker. The experimental result showed that the stability of repetition rate reached 3.0×10-12@1s and the stability of carrier envelop offset reached 1.0×10-10@1s. The initial experiment showed that measurement error was less than 1ppm. Later the error compensation module was introduced, and the optoelectronic aiming and tracking control module was built. The actual test result showed that the stability of miss distance was better than 2.0 μm, the tracking speed could reach 2m/s.

  4. Tesla coil discharges guided by femtosecond laser filaments in air

    NASA Astrophysics Data System (ADS)

    Brelet, Yohann; Houard, Aurélien; Arantchouk, Leonid; Forestier, Benjamin; Liu, Yi; Prade, Bernard; Carbonnel, Jérôme; André, Yves-Bernard; Mysyrowicz, André

    2012-04-01

    A Tesla coil generator was designed to produce high voltage pulses oscillating at 100 kHz synchronisable with a nanosecond temporal jitter. Using this compact high voltage generator, we demonstrate reproducible meter long discharges in air at a repetition rate of 1 Hz. Triggering and guiding of the discharges are performed in air by femtosecond laser filaments.

  5. Sub-micron structuring of silicon using femtosecond laser interferometry

    NASA Astrophysics Data System (ADS)

    Oliveira, V.; Vilar, R.; Serra, R.; Oliveira, J. C.; Polushkin, N. I.; Conde, O.

    2013-12-01

    We report the fabrication of planar sub-micron gratings in silicon with a period of 720 nm using a modified Michelson interferometer and femtosecond laser radiation. The gratings consist of alternated stripes of laser ablated and unmodified material. Ablated stripes are bordered by parallel ridges which protrude above the unmodified material. In the regions where ridges are formed, the laser radiation intensity is not sufficient to cause ablation. Nevertheless, melting and a significant temperature increase are expected, and ridges may be formed due to expansion of silicon during resolidification or silicon oxidation. These conclusions are consistent with the evolution of the stripes morphology as a function of the distance from the center of the grating. Sub-micron gratings were created in silicon using femtosecond laser radiation. A modified Michelson interferometer was used. The gratings consist of alternated stripes of ablated and unmodified material. Ablated stripes are surrounded by ridges which protrude above unmodified surface.

  6. Reflection of femtosecond laser light in multipulse ablation of metals

    SciTech Connect

    Vorobyev, A. Y.; Guo Chunlei

    2011-08-15

    The shot-to-shot reflectance of high-intensity laser light is studied as a function of both the number of laser shots and laser fluence in multipulse ablation of a metal when the irradiated surface undergoes structural changes from an initially smooth surface to a deep crater. Our study shows that the reflectance of the irradiated surface significantly decreases due to the high intensity of laser pulses and the laser-induced surface structures in ablation regimes typically used for femtosecond laser processing of materials. The high-intensity effect dominates in the reflection reduction at low numbers of laser shots when laser-induced surface structures do not cause the reflectance to decrease noticeably. With increasing the number of laser shots, the structural effect comes into play, and both high-intensity and structural effects quickly reduce the reflectance of the sample to a low value.

  7. Platinum nanostructures formed by femtosecond laser irradiation in water

    SciTech Connect

    Huo Haibin; Shen Mengyan

    2012-11-15

    Platinum nanostructures with various morphologies, such as spike-like, ripple-like and array-like structures, have been fabricated by 400 nm and 800 nm femtosecond laser irradiation in water. Different structures can be formed on the surfaces as a function of the laser wavelength, the fluence and scan methods. The reflectance measurements of these structures show much larger absorption on the irradiated surfaces than untreated platinum surfaces.

  8. Probing Molecular Dynamics at Attosecond Resolution with Femtosecond Laser Pulses

    NASA Astrophysics Data System (ADS)

    Tong, X. M.; Zhao, Z. X.; Lin, C. D.

    2003-12-01

    The kinetic energy distribution of D+ ions resulting from the interaction of a femtosecond laser pulse with D2 molecules is calculated based on the rescattering model. From analyzing the molecular dynamics, it is shown that the recollision time between the ionized electron and the D+2 ion can be read from the D+ kinetic energy peaks to attosecond accuracy. We further suggest that a more precise reading of the clock can be achieved by using shorter fs laser pulses (about 15fs).

  9. Tailoring the plasma channel generated by femtosecond laser pulse

    NASA Astrophysics Data System (ADS)

    Wang, Haitao; Fan, Chengyu; Zhang, Pengfei; Jia, Wei

    2015-02-01

    By investigating the spatial and temporal variations of the propagating pulses, we have shown for the first time that the lattice waveguides can induce nonlinear effects to tailor the plasma channel generated by a femtosecond laser pulse. Different types of the spatiotemporal localized nonlinear light bullet’s propagating configurations have been predicted. By adjusting the parameters of the modulation potential, longer continuum filaments and reshaped laser pulses can be obtained, due to the focusing nonlinearity of the lattice modulation index.

  10. Materials processing with a tightly focused femtosecond laser vortex pulse.

    PubMed

    Hnatovsky, Cyril; Shvedov, Vladlen G; Krolikowski, Wieslaw; Rode, Andrei V

    2010-10-15

    In this Letter we present the first (to our knowledge) demonstration of material modification using tightly focused single femtosecond laser vortex pulses. Double-charge femtosecond vortices were synthesized with a polarization-singularity beam converter based on light propagation in a uniaxial anisotropic medium and then focused using moderate- and high-NA optics (viz., NA=0.45 and 0.9) to ablate fused silica and soda-lime glass. By controlling the pulse energy, we consistently machine micrometer-size ring-shaped structures with <100nm uniform groove thickness. PMID:20967085

  11. High-power synchronously pumped femtosecond Raman fiber laser.

    PubMed

    Churin, D; Olson, J; Norwood, R A; Peyghambarian, N; Kieu, K

    2015-06-01

    We report a high-power synchronously pumped femtosecond Raman fiber laser operating in the normal dispersion regime. The Raman laser is pumped by a picosecond Yb(3+)-doped fiber laser. It produces highly chirped pulses with energy up to 18 nJ, average power of 0.76 W and 88% efficiency. The pulse duration is measured to be 147 fs after external compression. We observed two different regimes of operation of the laser: coherent and noise-like regime. Both regimes were experimentally characterized. Numerical simulations are in a good agreement with experimental results. PMID:26030549

  12. Intensity clamping in the filament of femtosecond laser radiation

    SciTech Connect

    Kandidov, V P; Fedorov, V Yu; Tverskoi, O V; Kosareva, O G; Chin, S L

    2011-04-30

    We have studied numerically the evolution of the light field intensity and induced refractive index of a medium upon filamentation of femtosecond laser radiation in air. It is shown that the intensity clamping results from the dynamic balance of optical powers of nonlinear lenses, induced by radiation due to the Kerr nonlinearity of air, and laser plasma produced during photoionisation. We have found the relation between the peak values of the light field intensity and the electron density in laser-produced plasma, as well as the transverse sizes of the filament and the plasma channel. (effects of laser radiation on matter)

  13. Ocular safety limits for 1030nm femtosecond laser cataract surgery

    NASA Astrophysics Data System (ADS)

    Wang, Jenny; Sramek, Christopher; Paulus, Yannis M.; Lavinsky, Daniel; Schuele, Georg; Anderson, Dan; Dewey, David; Palanker, Daniel V.

    2013-03-01

    Application of femtosecond lasers to cataract surgery has added unprecedented precision and reproducibility but ocular safety limits for the procedure are not well-quantified. We present an analysis of safety during laser cataract surgery considering scanned patterns, reduced blood perfusion, and light scattering on residual bubbles formed during laser cutting. Experimental results for continuous-wave 1030 nm irradiation of the retina in rabbits are used to calibrate damage threshold temperatures and perfusion rate for our computational model of ocular heating. Using conservative estimates for each safety factor, we compute the limits of the laser settings for cataract surgery that optimize procedure speed within the limits of retinal safety.

  14. Testing of a femtosecond pulse laser in outer space

    PubMed Central

    Lee, Joohyung; Lee, Keunwoo; Jang, Yoon-Soo; Jang, Heesuk; Han, Seongheum; Lee, Sang-Hyun; Kang, Kyung-In; Lim, Chul-Woo; Kim, Young-Jin; Kim, Seung-Woo

    2014-01-01

    We report a test operation of an Er-doped fibre femtosecond laser which was conducted for the first time in outer space. The fibre-based ultrashort pulse laser payload was designed to meet space-use requirements, undergone through ground qualification tests and finally launched into a low-earth orbit early in 2013. Test results obtained during a one-year mission lifetime confirmed stable mode-locking all the way through although the radiation induced attenuation (RIA) in the Er-doped gain fibre caused an 8.6% reduction in the output power. This successful test operation would help facilitate diverse scientific and technological applications of femtosecond lasers in space and earth atmosphere in the near future. PMID:24875665

  15. Femtosecond-laser assisted cataract surgery: a review.

    PubMed

    Abouzeid, Hana; Ferrini, Walter

    2014-11-01

    Introduced in 2008, the femtosecond laser is a promising new technological advance which plays an ever increasing role in cataract surgery where it automates the three main surgical steps: corneal incision, capsulotomy and lens fragmentation. The proven advantages over manual surgery are: a better quality of incision with reduced induced astigmatism; increased reliability and reproducibility of the capsulotomy with increased stability of the implanted lens; a reduction in the use of ultrasound. Regarding refractive results or safety, however, no prospective randomized study to date has shown significant superiority compared with standard manual technique. The significant extra cost generated by this laser, undertaken by the patient, is a limiting factor for both its use and study. This review outlines the potential benefits of femtosecond-laser-assisted cataract surgery due to the automation of key steps and the safety of this new technology. PMID:24835818

  16. Testing of a femtosecond pulse laser in outer space

    NASA Astrophysics Data System (ADS)

    Lee, Joohyung; Lee, Keunwoo; Jang, Yoon-Soo; Jang, Heesuk; Han, Seongheum; Lee, Sang-Hyun; Kang, Kyung-In; Lim, Chul-Woo; Kim, Young-Jin; Kim, Seung-Woo

    2014-05-01

    We report a test operation of an Er-doped fibre femtosecond laser which was conducted for the first time in outer space. The fibre-based ultrashort pulse laser payload was designed to meet space-use requirements, undergone through ground qualification tests and finally launched into a low-earth orbit early in 2013. Test results obtained during a one-year mission lifetime confirmed stable mode-locking all the way through although the radiation induced attenuation (RIA) in the Er-doped gain fibre caused an 8.6% reduction in the output power. This successful test operation would help facilitate diverse scientific and technological applications of femtosecond lasers in space and earth atmosphere in the near future.

  17. Application of femtosecond-laser induced nanostructures in optical memory.

    PubMed

    Shimotsuma, Yasuhiko; Sakakura, Masaaki; Miura, Kiyotaka; Qiu, Jiarong; Kazansky, Peter G; Fujita, Koji; Hirao, Kazuyuki

    2007-01-01

    The femtosecond laser induced micro- and nanostructures for the application to the three-dimensional optical data storage are investigated. We have observed the increase of refractive index due to local densification and atomic defect generation, and demonstrated the real time observation of photothermal effect after the femtosecond laser irradiation inside a glass by the transient lens (TrL) method. The TrL signal showed a damped oscillation with about an 800 ps period. The essential feature of the oscillation can be reproduced by the pressure wave creation and propagation to the outward direction from the irradiated region. The simulation based on elastodynamics has shown that a large thermoelastic stress is relaxed by the generation of the pressure wave. In the case of soda-lime glass, the velocity of the pressure wave is almost same as the longitudinal sound velocity at room temperature (5.8 microm/ns). We have also observed the localized photo-reduction of Sm3+ to Sm2+ inside a transparent and colorless Sm(3+)-doped borate glass. Photoluminescence spectra showed that some the Sm3+ ions in the focal spot within the glass sample were reduced to Sm2+ ions after femtosecond laser irradiation. A photo-reduction bit of 200 nm in three-dimensions can be recorded with a femtosecond laser and readout clearly by detecting the fluorescence excited by Ar+ laser (lambda = 488 nm). A photo-reduction bit can be also erased by photo-oxidation with a cw Ar+ laser (lambda = 514.5 nm). Since photo-reduction bits can be spaced 150 nm apart in a layer within glass, a memory capacity of as high as 1 Tbit can be achieved in a glass piece with dimensions of 10 mm x 10 mm x 1 mm. We have also demonstrated the first observation of the polarization-dependent periodic nanostructure formation by the interference between femtosecond laser light and electron acoustic waves. The observed nanostructures are the smallest embedded structures ever created by light. The period of self

  18. Intraocular Lens Fragmentation Using Femtosecond Laser: An In Vitro Study

    PubMed Central

    Bala, Chandra; Shi, Jeffrey; Meades, Kerrie

    2015-01-01

    Purpose: To transect intraocular lenses (IOLs) using a femtosecond laser in cadaveric human eyes. To determine the optimal in vitro settings, to detect and characterize gasses or particles generated during this process. Methods: A femtosecond laser was used to transect hydrophobic and hydrophilic acrylic lenses. The settings required to enable easy separation of the lens fragment were determined. The gasses and particles generated were analysed using gas chromatography mass spectrometer (GC-MS) and total organic carbon analyzer (TOC), respectively. Results: In vitro the IOL fragments easily separated at the lowest commercially available energy setting of 1 μJ, 8-μm spot, and 2-μm line separation. No particles were detected in the 0.5- to 900-μm range. No significant gasses or other organic breakdown by products were detected at this setting. At much higher energy levels 12 μJ (4 × 6 μm spot and line separation) significant pyrolytic products were detected, which could be harmful to the eye. In cadaveric explanted IOL capsule complex the laser pulses could be applied through the capsule to the IOL and successfully fragment the IOL. Conclusion: IOL transection is feasible with femtosecond lasers. Further in vivo animal studies are required to confirm safety. Translational Relevance: In clinical practice there are a number of large intraocular lenses that can be difficult to explant. This in-vitro study examines the possibility of transecting the lasers quickly using femtosecond lasers. If in-vivo studies are successful, then this innovation could help ophthalmic surgeons in IOL explantation. PMID:26101721

  19. Studying femtosecond-laser hyperdoping by controlling surface morphology

    SciTech Connect

    Winkler, Mark T.; Sher, Meng-Ju; Lin Yuting; Zhang, Haifei; Smith, Matthew J.; Gradecak, Silvija; Mazur, Eric

    2012-05-01

    We study the fundamental properties of femtosecond-laser (fs-laser) hyperdoping by developing techniques to control the surface morphology following laser irradiation. By decoupling the formation of surface roughness from the doping process, we study the structural and electronic properties of fs-laser doped silicon. These experiments are a necessary step toward developing predictive models of the doping process. We use a single fs-laser pulse to dope silicon with sulfur, enabling quantitative secondary ion mass spectrometry, transmission electron microscopy, and Hall effect measurements. These measurements indicate that at laser fluences at or above 4 kJ m{sup -2}, a single laser pulse yields a sulfur dose >(3 {+-} 1) x 10{sup 13} cm{sup -2} and results in a 45-nm thick amorphous surface layer. Based on these results, we demonstrate a method for hyperdoping large areas of silicon without producing the surface roughness.

  20. Porcine cadaver iris model for iris heating during corneal surgery with a femtosecond laser

    NASA Astrophysics Data System (ADS)

    Sun, Hui; Fan, Zhongwei; Wang, Jiang; Yan, Ying; Juhasz, Tibor; Kurtz, Ron

    2015-03-01

    Multiple femtosecond lasers have now been cleared for use for ophthalmic surgery, including for creation of corneal flaps in LASIK surgery. Preliminary study indicated that during typical surgical use, laser energy may pass beyond the cornea with potential effects on the iris. As a model for laser exposure of the iris during femtosecond corneal surgery, we simulated the temperature rise in porcine cadaver iris during direct illumination by the femtosecond laser. Additionally, ex-vivo iris heating due to femtosecond laser irradiation was measured with an infrared thermal camera (Fluke corp. Everett, WA) as a validation of the simulation.

  1. Nanosecond component in a femtosecond laser pulse

    SciTech Connect

    Shneider, M. N.; Semak, V. V.; Zhang Zhili

    2012-11-15

    Experimental and computational results show that the coherent microwave scattering from a laser-induced plasma can be used for measuring the quality of a fs laser pulse. The temporal dynamics of the microwave scattered signal from the fs-laser induced plasma can be related to the effect of nanosecond tail of the fs laser pulse.

  2. Measurements of Intense Femtosecond Laser Pulse Propagation in Air

    NASA Astrophysics Data System (ADS)

    Ting, Antonio

    2004-11-01

    Intense femtosecond pulses generated from chirped pulse amplification (CPA) lasers can deliver laser powers many times above the critical power for self-focusing in air. Catastrophic collapse of the laser pulse is usually prevented by the defocusing of the plasma column formed when the laser intensity gets above the threshold for multiphoton ionization. The resultant laser/plasma filament can extend many meters as the laser pulse propagates in the atmosphere. We have carried out a series of experiments both for understanding the formation mechanisms of the filaments and the nonlinear effects such as white light and harmonics generation associated with them. Many applications of these filaments such as remote atmospheric breakdown, laser induced electrical discharge and femtosecond laser material interactions require direct measurements of their characteristics. Direct measurements of these filaments had been difficult because the high laser intensity ( ˜10^13 W/cm^2) can damage practically any optical diagnostics. A novel technique was invented to obtain the first absolute measurements of laser energy, transverse profile, fluence and spectral content of the filaments. We are investigating a ``remote atmospheric breakdown'' concept of remotely sensing chemical and biological compounds. A short intense laser pulse can be generated at a remote position by using the group velocity dispersion (GVD) of the air to compress an initially long, frequency negatively chirped laser pulse to generate the air breakdown and filaments. We have observed that nonlinear contributions to the laser spectrum through self-phase modulation can lead to modification of the linear GVD compression. We have also observed the generation of ultraviolet (UV) radiations from these filaments in air and the induced fluorescence by the UV radiation of a surrogate biological agent. These and other results such as laser induced electrical discharges will be presented.

  3. Femtosecond mode-locked holmium fiber laser pumped by semiconductor disk laser.

    PubMed

    Chamorovskiy, A; Marakulin, A V; Ranta, S; Tavast, M; Rautiainen, J; Leinonen, T; Kurkov, A S; Okhotnikov, O G

    2012-05-01

    We report on a 2085 nm holmium-doped silica fiber laser passively mode-locked by semiconductor saturable absorber mirror and carbon nanotube absorber. The laser, pumped by a 1.16 μm semiconductor disk laser, produces 890 femtosecond pulses with the average power of 46 mW and the repetition rate of 15.7 MHz. PMID:22555700

  4. Polarization behaviour of femtosecond laser written waveguides in lithium niobate

    NASA Astrophysics Data System (ADS)

    Tejerina, M. R.; Biasetti, D. A.; Torchia, G. A.

    2015-09-01

    In this work, we analysed the polarization of guided light in femtosecond laser written waveguides. The studied waveguides were performed with different laser pulse energies in an x-cut lithium niobate crystal. The guided intensities were experimentally measured and compared with numerical simulations reaching a qualitatively good accordance. This comparison allowed a verification of the "mechanical expansion theory" which is useful to compute the refractive index field. Also, information related to the modelling of waveguides generated with different laser pulse energies was obtained. Both of these facts are keys to design and manufacture optical circuits by using this technological approach.

  5. Femtosecond laser additive manufacturing of iron and tungsten parts

    NASA Astrophysics Data System (ADS)

    Nie, Bai; Yang, Lihmei; Huang, Huan; Bai, Shuang; Wan, Peng; Liu, Jian

    2015-06-01

    For the first time, femtosecond laser additive manufacturing is demonstrated. Pure iron and tungsten powders, having very different melting temperature and mechanical properties, are used for the demonstration. Parts with various shapes, such as ring and cube, are fabricated. Micro-hardness and ultimate tensile strength are investigated for the fabricated samples. The results are also compared to the similar parts made by a continuous-wave laser. It is found that fs laser additive manufacturing can obtain better mechanical properties and fabricate materials that are not possible before.

  6. Polymer hydrophilicity and hydrophobicity induced by femtosecond laser direct irradiation

    NASA Astrophysics Data System (ADS)

    Wang, Z. K.; Zheng, H. Y.; Lim, C. P.; Lam, Y. C.

    2009-09-01

    Controlled modification of surface wettability of polymethyl methacrylate (PMMA) was achieved by irradiation of PMMA surface with femtosecond laser pulses at various laser fluences and focus distances. Fluences from 0.40 to 2.1 J/cm2 produced a hydrophobic surface and 2.1 to 52.7 J/cm2 (maximum investigated) produced a hydrophilic surface. Fluences less than 0.31 J/cm2 had no effect on the wettability of the raw PMMA. This change in wettability was caused dominantly by laser induced chemical structure modification and not by a change in surface roughness.

  7. High-resolution optical frequency metrology with stabilized femtosecond lasers

    NASA Astrophysics Data System (ADS)

    Jones, Ronald Jason

    The merging of such seemingly disparate fields as optical frequency metrology and ultrafast physics over the past few years has had a revolutionary impact on both fields. Extensive research over the past several decades has focused on stabilizing cw lasers to atomic and molecular transitions. These transitions in the optical and near-infrared regimes provide some of the highest Q's accessible in spectroscopy due to their high resonant frequencies (Q ≡ nu o/deltanu). Modern experiments have enjoyed increasing levels of precision and accuracy due to such stabilized laser systems. A long standing problem in optical frequency metrology, however, is the difficulty to perform direct frequency measurements in the optical spectrum. Traditional optical frequency chains are complex, costly, and lack flexibility. Recent experiments based on mode-locked femtosecond (fs) lasers promise to eliminate this problem and make optical frequency measurements accessible as a general laboratory tool. The use of fs lasers now enables the direct measurement of optical transitions by simply linking these frequencies to the repetition rate of the fs laser. The ability of the femtosecond laser to link the optical and radio frequency regimes is ultimately limited by its stability. In this dissertation, we present a novel stabilization scheme in which the frequency, phase, and repetition rate of a Kerr-lens mode-locked (KLM) ti:sapphire laser are locked to that of an ultra-stable Fabry-Perot reference cavity. The large signal to noise ratio of the recovered cavity resonance allows the superb short term stability (tau < 1 second) of the passive reference cavity to be transferred to the femtosecond laser. This technique may find future application in any experiment involving the use of femtosecond pulses in which a resonant cavity is employed, such as intracavity studies of light-matter interactions with ultra-short pulses. The short term instability of the cavity stabilized femtosecond laser

  8. Femtosecond laser direct writing of monocrystalline hexagonal silver prisms

    SciTech Connect

    Vora, Kevin; Kang, SeungYeon; Moebius, Michael; Mazur, Eric

    2014-10-06

    Bottom-up growth methods and top-down patterning techniques are both used to fabricate metal nanostructures, each with a distinct advantage: One creates crystalline structures and the other offers precise positioning. Here, we present a technique that localizes the growth of metal crystals to the focal volume of a laser beam, combining advantages from both approaches. We report the fabrication of silver nanoprisms—hexagonal nanoscale silver crystals—through irradiation with focused femtosecond laser pulses. The growth of these nanoprisms is due to a nonlinear optical interaction between femtosecond laser pulses and a polyvinylpyrrolidone film doped with silver nitrate. The hexagonal nanoprisms have bases hundreds of nanometers in size and the crystal growth occurs over exposure times of less than 1 ms (8 orders of magnitude faster than traditional chemical techniques). Electron backscatter diffraction analysis shows that the hexagonal nanoprisms are monocrystalline. The fabrication method combines advantages from both wet chemistry and femtosecond laser direct-writing to grow silver crystals in targeted locations. The results presented in this letter offer an approach to directly positioning and growing silver crystals on a substrate, which can be used for plasmonic devices.

  9. Laser surface and subsurface modification of sapphire using femtosecond pulses

    NASA Astrophysics Data System (ADS)

    Eberle, G.; Schmidt, M.; Pude, F.; Wegener, K.

    2016-08-01

    Two methods to process sapphire using femtosecond laser pulses are demonstrated, namely ablation (surface), and in-volume laser modification followed by wet etching (subsurface). Firstly, the single and multipulse ablation threshold is determined and compared with previous literature results. A unique application of ablation is demonstrated by modifying the entrance aperture of water jet orifices. Laser ablation exhibits advantages in terms of geometric flexibility and resolution, however, defects in the form of edge outbreaks and poor surface quality are evident. Secondly, the role of material transformation, polarisation state and formation of multi-focus structures after in-volume laser modification is investigated in order to explain their influence during the wet etching process. Laser scanning and electron microscopy as well as electron backscatter diffraction measurements supported by ion beam polishing are used to better understand quality and laser-material interactions of the two demonstrated methods of processing.

  10. Fabrication of mitigation pits for improving laser damage resistance in dielectric mirrors by femtosecond laser machining

    SciTech Connect

    Wolfe, Justin E.; Qiu, S. Roger; Stolz, Christopher J.

    2011-03-20

    Femtosecond laser machining is used to create mitigation pits to stabilize nanosecond laser-induced damage in multilayer dielectric mirror coatings on BK7 substrates. In this paper, we characterize features and the artifacts associated with mitigation pits and further investigate the impact of pulse energy and pulse duration on pit quality and damage resistance. Our results show that these mitigation features can double the fluence-handling capability of large-aperture optical multilayer mirror coatings and further demonstrate that femtosecond laser macromachining is a promising means for fabricating mitigation geometry in multilayer coatings to increase mirror performance under high-power laser irradiation.

  11. Synchronized videography of plasma plume expansion during femtosecond laser ablation

    NASA Astrophysics Data System (ADS)

    Paolasini, Steven; Kietzig, Anne

    2014-03-01

    Femtosecond lasers are gaining industrial interest for surface patterning and structuring because of the reduced heat effects to the surrounding material, resulting in a good quality product with a high aspect ratio. Analysis of the plasma plume generated during ablation can provide useful information about the laser-material interactions and thereby the quality of the resulting surface patterns. As a low-cost alternative to rather complicated ICCD camera setups, presented here is an approach based on filming the laser machining process with a high speed camera and tuning the frame rate of the camera to slightly lower than the laser pulse frequency. The delay in frequency between the laser and camera results in frames taken from sequential pulses. Each frame represents a later phase of plume expansion although taken from different pulses. Assuming equal plume evolution processes from pulse to pulse, the sequence of images obtained completes a plume expansion video. To test the assumption of homogeneity between sequential plumes, the camera can be tuned to the frequency of the laser, as to capture consecutive plumes at the same phase in their evolution. This approach enables a relatively low-cost, high resolution visualization of plasma plume evolution suitable for industrial micromachining applications with femtosecond lasers. Using this approach we illustrate differences in plume expansion at the example of machining homogeneous surface patterns in different liquid and gaseous processing environments.

  12. Femtosecond all-solid-state laser for refractive surgery

    NASA Astrophysics Data System (ADS)

    Zickler, Leander; Han, Meng; Giese, G.'nter; Loesel, Frieder H.; Bille, Josef F.

    2003-06-01

    Refractive surgery in the pursuit of perfect vision (e.g. 20/10) requires firstly an exact measurement of abberations induced by the eye and then a sophisticated surgical approach. A recent extension of wavefront measurement techniques and adaptive optics to ophthalmology has quantitatively characterized the quality of the human eye. The next milestone towards perfect vision is developing a more efficient and precise laser scalpel and evaluating minimal-invasive laser surgery strategies. Femtosecond all-solid-state MOPA lasers based on passive modelocking and chirped pulse amplification are excellent candidates for eye surgery due to their stability, ultra-high intensity and compact tabletop size. Furthermore, taking into account the peak emission in the near IR and diffraction limited focusing abilities, surgical laser systems performing precise intrastromal incisions for corneal flap resection and intrastromal corneal reshaping promise significant improvement over today's Photorefractive Keratectomy (PRK) and Laser Assisted In Situ Keratomileusis (LASIK) techniques which utilize UV excimer lasers. Through dispersion control and optimized regenerative amplification, a compact femtosecond all-solid-state laser with pulsed energy well above LIOB threshold and kHz repetition rate is constructed. After applying a pulse sequence to the eye, the modified corneal morphology is investigated by high resolution microscopy (Multi Photon/SHG Confocal Microscope).

  13. Optical cell cleaning with NIR femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Uchugonova, Aisada; Breunig, Hans Georg; Batista, Ana; König, Karsten

    2015-03-01

    Femtosecond laser microscopes have been used as both micro and nanosurgery tools. The optical knock-out of undesired cells in multiplex cell clusters shall be further reported on in this study. Femtosecond laser-induced cell death is beneficial due to the reduced collateral side effects and therefore can be used to selectively destroy target cells within monolayers, as well as within 3D tissues, all the while preserving cells of interest. This is an important characteristic for the application in stem cell research and cancer treatment. Non-precise damage compromises the viability of neighboring cells by inducing side effects such as stress to the cells surrounding the target due to the changes in the microenvironment, resulting from both the laser and laser-exposed cells. In this study, optimum laser parameters for optical cleaning by isolating single cells and cell colonies are exploited through the use of automated software control. Physiological equilibrium and cellular responses to the laser induced damages are also investigated. Cell death dependence on laser focus, determination and selectivity of intensity/dosage, controllable damage and cell recovery mechanisms are discussed.

  14. Rapid microfabrication of transparent materials using filamented femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Butkus, S.; Gaižauskas, E.; Paipulas, D.; Viburys, Ž.; Kaškelyė, D.; Barkauskas, M.; Alesenkov, A.; Sirutkaitis, V.

    2014-01-01

    Microfabrication of transparent materials using femtosecond laser pulses has showed good potential towards industrial application. Maintaining pulse energies exceeding the critical self-focusing threshold by more than 100-fold produced filaments that were used for micromachining purposes. This article demonstrates two different micromachining techniques using femtosecond filaments generated in different transparent media (water and glass). The stated micromachining techniques are cutting and welding of transparent samples. In addition, cutting and drilling experiments were backed by theoretical modelling giving a deeper insight into the whole process. We demonstrate cut-out holes in soda-lime glass having thickness up to 1 mm and aspect ratios close to 20, moreover, the fabrication time is of the order of tens of seconds, in addition, grooves and holes were fabricated in hardened 1.1 mm thick glass (Corning Gorilla glass). Glass welding was made possible and welded samples were achieved after several seconds of laser fabrication.

  15. Beam wandering of femtosecond laser filament in air.

    PubMed

    Yang, Jing; Zeng, Tao; Lin, Lie; Liu, Weiwei

    2015-10-01

    The spatial wandering of a femtosecond laser filament caused by the filament heating effect in air has been studied. An empirical formula has also been derived from the classical Karman turbulence model, which determines quantitatively the displacement of the beam center as a function of the propagation distance and the effective turbulence structure constant. After fitting the experimental data with this formula, the effective turbulence structure constant has been estimated for a single filament generated in laboratory environment. With this result, one may be able to estimate quantitatively the displacement of a filament over long distance propagation and interpret the practical performance of the experiments assisted by femtosecond laser filamentation, such as remote air lasing, pulse compression, high order harmonic generation (HHG), etc. PMID:26480079

  16. Femtosecond laser fluorescence and propagation in very dense potassium vapor.

    PubMed

    Makdisi, Y; Kokaj, J; Afrousheh, K; Nair, R; Mathew, J; Pichler, G

    2013-12-16

    Femtosecond (fs) laser propagation and fluorescence of dense potassium vapor was studied, and the spectral region around the first and the second doublets of the principal series lines of potassium atoms was investigated. In our search we did not observe the conical emission in the far field, although it was previously observed in the case of rubidium. We discuss the possible reason of this unexpected result. The fluorescence spectrum revealed Rb impurity resonance lines in emission due to the collisional redistribution from the K(4p) levels into the Rb(5p) levels. In the forward propagation of 400 nm femtosecond light we observed the molecular band red shifted from potassium second doublet. However, no molecular spectrum was observed when the mode-locked fs laser light was discretely tuned within the wings of the first resonance lines, at 770 nm. PMID:24514609

  17. Ultrahigh-Resolution Optical Coherence Tomography Using Femtosecond Lasers

    NASA Astrophysics Data System (ADS)

    Fujimoto, J. G.; Aguirre, A. D.; Chen, Y.; Herz, P. R.; Hsiung, P.-L.; Ko, T. H.; Nishizawa, N.; Kärtner, F. X.

    Optical coherence tomography (OCT) is an emerging optical imaging modality for biomedical research and clinical medicine. OCT can perform high resolution, cross-sectional tomographic imaging in materials and biological systems by measuring the echo time delay and magnitude of backreflected or backscattered light [1]. In medical applications, OCT has the advantage that imaging can be performed in situ and in real time, without the need to remove and process specimens as in conventional excisional biopsy and histopathology. OCT can achieve axial image resolutions of 1 to 15 μm; one to two orders of magnitude higher than standard ultrasound imaging. The image resolution in OCT is determined by the coherence length of the light source and is inversely proportional to its bandwidth. Femtosecond lasers can generate extremely broad bandwidths and have enabled major advances in ultrahigh-resolution OCT imaging. This chapter provides an overview of OCT technology and ultrahigh-resolution OCT imaging using femtosecond lasers.

  18. Femtosecond laser dissection in C. elegans neural circuits

    NASA Astrophysics Data System (ADS)

    Samuel, Aravinthan D. T.; Chung, Samuel H.; Clark, Damon A.; Gabel, Christopher V.; Chang, Chieh; Murthy, Venkatesh; Mazur, Eric

    2006-02-01

    The nematode C. elegans, a millimeter-long roundworm, is a well-established model organism for studies of neural development and behavior, however physiological methods to manipulate and monitor the activity of its neural network have lagged behind the development of powerful methods in genetics and molecular biology. The small size and transparency of C. elegans make the worm an ideal test-bed for the development of physiological methods derived from optics and microscopy. We present the development and application of a new physiological tool: femtosecond laser dissection, which allows us to selectively ablate segments of individual neural fibers within live C. elegans. Femtosecond laser dissection provides a scalpel with submicrometer resolution, and we discuss its application in studies of neural growth, regenerative growth, and the neural basis of behavior.

  19. Nanosecond and femtosecond laser spectroscopy of molecules of biological interest

    NASA Astrophysics Data System (ADS)

    Villani, P.; Orlando, S.; Santagata, A.; De Bonis, A.; Veronesi, S.; Giardini, A.

    2007-07-01

    This paper mainly concerns on nanosecond and femtosecond laser spectroscopy of aromatic organic compounds as neurotransmitters, and plume diagnostics of the ablated species, in order to characterize the plasma dynamics, i.e. the temporal and spatial evolution of the plume. Optical emission spectroscopy has been applied to characterize the transient species produced in the femtosecond (fs) and nanosecond (ns) regimes. The laser sources employed for optical emission spectroscopy are a frequency-doubled Nd:YAG Handy ( λ = 532 nm, τ = 5 ns) and a frequency-doubled Nd:glass ( λ = 527 nm, τ = 250 fs). These studies aim to detect and give information on the photoexcitation and photodissociation of these biological molecules and to compare the plasma characteristics in the two ablation regimes.

  20. Selective metallization on insulator surfaces with femtosecond laser pulses.

    PubMed

    Xu, Jian; Liao, Yang; Zeng, Huidan; Zhou, Zenghui; Sun, Haiyi; Song, Juan; Wang, Xinshun; Cheng, Ya; Xu, Zhizhan; Sugioka, Koji; Midorikawa, Katsumi

    2007-10-01

    We report selective metallization on surfaces of insulators (glass slides and lithium niobate crystal) based on femtosecond laser modification combined with electroless plating. The process is mainly composed of four steps: (1) formation of silver nitrate thin films on the surfaces of glass or crystal substrates; (2) generation of silver particles in the irradiated area by femtosecond laser direct writing; (3) removal of unirradiated silver nitrate films; and (4) selective electroless plating in the modified area. We discuss the mechanism of selective metallization on the insulators. Moreover, we investigate the electrical and adhesive properties of the copper microstructures patterned on the insulator surfaces, showing great potential of integrating electrical functions into lab-on-a-chip devices. PMID:19550542

  1. Optimization study of the femtosecond laser-induced forward-transfer process with thin aluminum films

    NASA Astrophysics Data System (ADS)

    Bera, Sudipta; Sabbah, A. J.; Yarbrough, J. M.; Allen, C. G.; Winters, Beau; Durfee, Charles G.; Squier, Jeff A.

    2007-07-01

    The parameters for an effective laser-induced forward-transfer (LIFT) process of aluminum thin films using a femtosecond laser are studied. Deposited feature size as a function of laser fluence, donor film thickness, quality of focus, and the pulse duration are varied, providing a metric of the most desirable conditions for femtosecond LIFT with thin aluminum films.

  2. Optimally enhanced optical emission in laser-induced air plasma by femtosecond double-pulse

    NASA Astrophysics Data System (ADS)

    Chen, Anmin; Li, Suyu; Li, Shuchang; Jiang, Yuanfei; Shao, Junfeng; Wang, Tingfeng; Huang, Xuri; Jin, Mingxing; Ding, Dajun

    2013-10-01

    In laser-induced breakdown spectroscopy, a femtosecond double-pulse laser was used to induce air plasma. The plasma spectroscopy was observed to lead to significant increase of the intensity and reproducibility of the optical emission signal compared to femtosecond single-pulse laser. In particular, the optical emission intensity can be optimized by adjusting the delay time of femtosecond double-pulse. An appropriate pulse-to-pulse delay was selected, that was typically about 50 ps. This effect can be especially advantageous in the context of femtosecond laser-induced breakdown spectroscopy, plasma channel, and so on.

  3. Optimally enhanced optical emission in laser-induced air plasma by femtosecond double-pulse

    SciTech Connect

    Chen, Anmin; Li, Suyu; Li, Shuchang; Jiang, Yuanfei; Ding, Dajun; Shao, Junfeng; Wang, Tingfeng; Huang, Xuri; Jin, Mingxing

    2013-10-15

    In laser-induced breakdown spectroscopy, a femtosecond double-pulse laser was used to induce air plasma. The plasma spectroscopy was observed to lead to significant increase of the intensity and reproducibility of the optical emission signal compared to femtosecond single-pulse laser. In particular, the optical emission intensity can be optimized by adjusting the delay time of femtosecond double-pulse. An appropriate pulse-to-pulse delay was selected, that was typically about 50 ps. This effect can be especially advantageous in the context of femtosecond laser-induced breakdown spectroscopy, plasma channel, and so on.

  4. Experimental femtosecond laser photodisruption of rabbit sclera for minimally invasive laser sclerostomy: An in vitro study

    NASA Astrophysics Data System (ADS)

    Yang, Xiaobo; Dai, Nengli; Long, Hua; Lu, Peixiang; Li, Wan; Jiang, Fagang

    2010-07-01

    Femtosecond laser technology, used as a minimally invasive tool in intrastromal refractive surgery, may also have potential as a useful instrument for glaucoma filtration surgery. The purpose of the present study was to evaluate the feasibility of minimally invasive laser sclerostomy by femtosecond laser photodisruption and seek the appropriate patterns of laser ablation and relevant laser parameters. A femtosecond laser (800 nm/50 fs/1 kHz), focused by a 0.1 numerical aperture (NA) objective lens, with different pulse energies and exposure times was applied to ablate hydrated rabbit sclera in vitro. The irradiated samples were examined by scanning electron microscopy (SEM). By moving a three-dimensional, computer-controlled translation stage to which the sample was attached, the femtosecond laser could produce three types of ablation patterns, including linear ablation, cylindrical aperture and rectangular cavity. With pulse energies ranging from 37.5 to 150 μJ, the linear lesions were consistently observed at the inner surface of sclera, whereas it failed to make any photodisruption if pulse energy was below the threshold value of 31.25 μJ, with the corresponding threshold intensity of 4.06×10 14 W/cm 2. The depths of the linear lesions increased linearly with both pulse energy (37.5-150 μJ) and exposure time (0.1-0.4 s). Histological examination showed the incisions produced by femtosecond laser photodisruption had precise geometry and the edges were sharp and smooth, with no evidence of collateral damage to the surrounding tissue. Our results predict the potential application of femtosecond laser pulses in minimally invasive laser sclerostomy for glaucoma treatment.

  5. Multiterawatt femtosecond laser system with kilohertz pulse repetition rate

    SciTech Connect

    Petrov, V V; Pestryakov, E V; Laptev, A V; Petrov, V A; Kuptsov, G V; Trunov, V I; Frolov, S A

    2014-05-30

    The basic principles, layout and components are presented for a multiterawatt femtosecond laser system with a kilohertz pulse repetition rate f, based on their parametric amplification and laser amplification of picosecond radiation that pumps the stages of the parametric amplifier. The results of calculations for a step-by-step increase in the output power from the LBO crystal parametric amplifier channel up to the multiterawatt level are presented. By using the developed components in the pump channel of the laser system, the parameters of the regenerative amplifier with the output energy ∼1 mJ at the wavelength 1030 nm and with f = 1 kHz are experimentally studied. The optical scheme of the diode-pumped multipass cryogenic Yb:Y{sub 2}O{sub 3} laser ceramic amplifier is developed and its characteristics are determined that provide the output energy within the range 0.25 – 0.35 J. (lasers)

  6. Absence of amorphous phase in high power femtosecond laser-ablated silicon

    SciTech Connect

    Rogers, Matthew S.; Grigoropoulos, Costas P.; Minor, Andrew M.; Mao, Samuel S.

    2009-01-05

    As femtosecond lasers emerge as viable tools for advanced microscale materials processing, it becomes increasingly important to understand the characteristics of materials resulting from femtosecond laser microablation or micromachining. We conducted transmission electron microscopy experiments to investigate crater structures in silicon produced by repetitive high power femtosecond laser ablation. Comparable experiments of nanosecond laser ablation of silicon were also performed. We found that an amorphous silicon layer that is typically produced in nanosecond laser ablation is absent when the material is irradiated by high power femtosecond laser pulses. Instead, only a defective single crystalline layer was observed in the high power femtosecond laser-ablated silicon crater. Possible mechanisms underlying the formation of the defective single crystalline phase are discussed.

  7. Patterning of silica microsphere monolayers with focused femtosecond laser pulses

    SciTech Connect

    Cai Wenjian; Piestun, Rafael

    2006-03-13

    We demonstrate the patterning of monolayer silica microsphere lattices with tightly focused femtosecond laser pulses. We selectively removed microspheres from a lattice and characterized the effect on the lattice and the substrate. The proposed physical mechanism for the patterning process is laser-induced breakdown followed by ablation of material. We show that a microsphere focuses radiation in its interior and in the near field. This effect plays an important role in the patterning process by enhancing resolution and accuracy and by reducing the pulse energy threshold for damage. Microsphere patterning could create controlled defects within self-assembled opal photonic crystals.

  8. Femtosecond laser internal manufacturing of three-dimensional microstructure devices

    NASA Astrophysics Data System (ADS)

    Zheng, Chong; Hu, Anming; Chen, Tao; Oakes, Ken D.; Liu, Shibing

    2015-10-01

    Potential applications for three-dimensional microstructure devices developed rapidly across numerous fields including microoptics, microfluidics, microelectromechanical systems, and biomedical devices. Benefiting from many unique fabricating advantages, internal manufacturing methods have become the dominant process for three-dimensional microstructure device manufacturing. This paper provides a brief review of the most common techniques of femtosecond laser three-dimensional internal manufacturing (3DIM). The physical mechanisms and representative experimental results of 3D manufacturing technologies based on multiphoton polymerization, laser modification, microexplosion and continuous hollow structure internal manufacturing are provided in details. The important progress in emerging applications based on the 3DIM technologies is introduced as well.

  9. Variable bandwidth birefringent filter for tunable femtosecond lasers

    SciTech Connect

    Naganuma, K.; Lenz, G.; Ippen, E.P. )

    1992-10-01

    A design for a birefringent filter is described, which is suitable for tunable femtosecond lasers. Using a single plate, which has a steeply diving optic axis, two-octave tunability is attained with negligible deterioration of the stopband rejection. For a specific wavelength region, it means that the filter's bandwidth can be changed by a factor of four. Another characteristic of the design is that, for the same bandwidth, the proposed plate is five times thicker than a conventional plate in which the optic axis is parallel to the surface. Thus, etalon effects can be avoided. Tuning characteristics of color center lasers utilizing the new filter are also presented. 18 refs.

  10. 1-kHz-repetition-rate femtosecond Raman laser

    NASA Astrophysics Data System (ADS)

    Didenko, N. V.; Konyashchenko, A. V.; Kostryukov, P. V.; Losev, L. L.; Pazyuk, V. S.; Tenyakov, S. Yu

    2016-07-01

    A femtosecond Raman laser utilising compressed hydrogen is experimentally investigated under pumping by radiation from a 1-kHz-repetition-rate Ti : sapphire laser. In the regime of double-pulse pumping, the conditions are determined, which correspond to the minimal energy dispersion of Stokes pulses. The optical scheme is realised, which is capable of ensuring the long-term stability of the average power of the first Stokes component with a variation of less than 2%. The Stokes pulses are produced with a pulse duration of 60 fs and energy of 0.26 mJ at a conversion efficiency of 14%.

  11. A new approach to fabricate pdms structures using femtosecond laser

    NASA Astrophysics Data System (ADS)

    Selvaraj, Hamsapriya

    Polydimethylsiloxane (PDMS) is commonly used to prototype micro and nano featured components due to its beneficial properties. PDMS based devices have been used for diverse applications such as cell culturing, cell sorting and sensors. Motivated by such diverse applications possible through pure PDMS and reinforced PDMS, numerous efforts have been directed towards developing novel fabrication techniques. Prototyping 2D and 3D pure and reinforced PDMS microdevices normally require a long curing time and must go through multiple steps. This research explores the possibility of fabricating microscale and nanoscale structures directly from PDMS resin using femtosecond laser processing. This study offers an alternative fabrication route that potentially lead to a new way for prototyping of pure and reinforced PDMS devices, and the generation of hybrid nanomaterials. In depth investigation of femtosecond laser irradiation of PDMS resin reveals that the process is highly intensity-dependent. At low to intermediate intensity regime, femtosecond laser beam is able to rapidly cure the resin and create micron-sized structures directly from PDMS resin. At higher intensity regime, a total break-down of the resin material occurs and leads to the formation of PDMS nanoparticles. This work demonstrates a new way of rapid curing of PDMS resin on a microsecond timescale using femtosecond laser irradiation. The proposed technique permits maskless singlestep curing and is capable of fabricating 2D and 3D structures in micro-scale. Reinforced PDMS microstructures also have been fabricated through this method. The proposed technique permits both reinforcement and rapid curing and is ideal for fabricating reinforced structures in microscale. The strength of the nanofiber reinforced PDMS microstructures has been investigated by means of Nanoindentation test. The results showed significant improvement in strength of the material. Hybrid PDMS-Si and hybrid PDMS-Al nanoparticle aggregate

  12. Femtosecond laser collagen cross-linking without traditional photosensitizers

    NASA Astrophysics Data System (ADS)

    Guo, Yizang; Wang, Chao; Celi, Nicola; Vukelic, Sinisa

    2015-03-01

    Collagen cross-linking in cornea has the capability of enhancing its mechanical properties and thereby providing an alternative treatment for eye diseases such as keratoconus. Currently, riboflavin assisted UVA light irradiation is a method of choice for cross-link induction in eyes. However, ultrafast pulsed laser interactions may be a powerful alternative enabling in-depth treatment while simultaneously diminishing harmful side effects such as, keratocyte apoptosis. In this study, femtosecond laser is utilized for treatment of bovine cornea slices. It is hypothesized that nonlinear absorption of femtosecond laser pulses plays a major role in the maturation of immature cross-links and the promotion of their growth. Targeted irradiation with tightly focused laser pulses allows for the absence of a photosensitizing agent. Inflation test was conducted on half treated porcine cornea to identify the changes of mechanical properties due to laser treatment. Raman spectroscopy was utilized to study subtle changes in the chemical composition of treated cornea. The effects of treatment are analyzed by observing shifts in Amide I and Amide III bands, which suggest deformation of the collagen structure in cornea due to presence of newly formed cross-links.

  13. Saturable absorber mode-locked femtosecond Cr4+:YAG laser

    NASA Astrophysics Data System (ADS)

    Hayduk, Michael J.; Johns, Steven T.; Krol, Mark F.

    1997-07-01

    We have demonstrated self-starting passive mode-locking of a chromium-doped:YAG (Cr4+:YAG) laser using a saturable absorber mirror (SAM) structure. Highly stable femtosecond pulses tunable from 1488 to 1535 nm were generated. Average TEM00 output powers ranged from 40 to 80 mW with a minimum pulse width of 120 fs measured at 1488 nm. The generation of ultrashort pulses in solid-state lasers using the Kerr lens modelocking (KLM) technique has been the center of much attention in recent years. Sub 100 fs pulses have been produced using many different laser systems. However, the KLM process is very sensitive to cavity alignment and is easily perturbed by mechanical vibrations and pump power fluctuations. A more reliable process makes use of a saturable absorber to start and stabilize the soliton formation process. The saturable absorber eliminates the need for critical cavity alignment. The femtosecond pulse train produced by the SAM structure in the Cr4+:YAG laser system is highly stable over very long periods of time. The wide tunability of the Cr4+:YAG laser throughout the 1.5 micrometer transmission window of optical fiber makes it an ideal spectroscopic source for the characterization and development of novel materials and devices for ultrafast optical interconnects.

  14. Nonequilibrium screening and exciton dynamics probed by femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Peyghambarian, N.; Koch, S. W.

    1993-02-01

    Our efforts were aimed at the study of nonequilibrium properties of a high-density electron-hole-pair system, which was generated resonantly by femtosecond laser excitation. The investigation consisted of joint theoretical and experimental approaches. Using state of the art femtosecond experimental techniques, we studied extremely rapid physical phenomena. We have succeeded not only in completing the proposed tasks, but have also initiated some new projects and obtained very interesting results. During the last three years in this program, we have published three physical Review Letters, nine Physical Reviews, several other papers in good journals such as Appl. Phys. Lett., J. Opt. Soc. Am., etc., nineteen invited presentations at important conferences, and several contributed papers at international conferences. The list of publications is given in the next section. Here, we summarize the highlights of our achievements during the last three years of this contract.

  15. [Objective evaluation the application of femtosecond laser in cataract surgery].

    PubMed

    Liu, Y Z

    2016-02-01

    Femtosecond laser-assisted cataract surgery (FLACS) is a novel technology and the biggest revolution in the field of cataract in the latest several years. However, increasing large-scale population randomized controlled trials (RCT) have demonstrated that FLACS does not provide significant advantages over conventional phacoemulsification cataract surgery (CPCS) for common cataract patients. Furthermore, the cost and space requirement of the femtosecond equipment are another two limitations for the universal application of FSL in cataract surgery. However, FLACS may be beneficial for complex cataract situations, such as lens dislocation, zonular laxity, traumatic cataract, low preoperative endothelial cell values, and significant corneal astigmatism. With the progress of science and technology, FLACS can be expected to achieve integration with phacoemulsification systems, and equipment costs can be reduced, making it more widely used in clinical practice in the future. PMID:26906700

  16. Crystalline micro/nanostructures fabrication on silicon using femtosecond laser

    NASA Astrophysics Data System (ADS)

    Deng, Guoliang; Yang, Xianheng; Feng, Guoying; Zhou, Shouhuan

    2015-02-01

    The laser induced micro/ nano-meter size surface structures are fabricated by multi linear polarized femtosecond laser pulses (pulse duration τ=35 fs, wavelength λ=800 nm) irradiation at room temperature(25 ° ) and 400 °. The structures fabricated at these two temperatures show distinct temperature dependence. The grooves, which are parallel to the polarization of the laser light, can be clearly observed at almost all the structured area formed at 400 ° while laser induced period structures(ripples) are the most pronounced surface structure in the crater formed at room temperature. The crystallinity of these surface structures are investigated by using Raman spectroscopy. The Raman spectrum shows that all the structured area formed at 400 ° is crystalline(or poly-crystalline) while amorphous silicon can be observed within the structures formed at room temperature (25 °). These results indicate that temperature is an important parameter to be tuned to tailor the micro/nano-structure fabrication.

  17. Femtosecond laser generated gold nanoparticles and their plasmonic properties

    NASA Astrophysics Data System (ADS)

    Das, Rupali; Navas M., P.; Soni, R. K.

    2016-05-01

    The pulsed laser ablation in liquid medium is now commonly used to generate stable colloidal nanoparticles (NPs) in absence of any chemical additives or stabilizer with diverse applications. In this paper, we report generation of gold NPs (Au NPs) by ultra-short laser pulses. Femtosecond (fs) laser radiation (λ = 800 nm) has been used to ablate a gold target in pure de-ionized water to produce gold colloids with smallsize distribution. The average size of the particles can be further controlled by subjecting to laser-induced post-irradiation providing a versatile physical method of size-selected gold nanoparticles. The optical extinction and morphological dimensions were investigated with UV-Vis spectroscopy and Transmission Electron Microscopy measurements, respectively. Finite difference time domain (FDTD) method is employed to calculate localized surface plasmon (LSPR) wavelength and the near-field generated by Au NPs and their hybrids.

  18. Oxygen assisted interconnection of silver nanoparticles with femtosecond laser radiation

    SciTech Connect

    Huang, H.; Zhou, Y.; Duley, W. W.

    2015-12-14

    Ablation of silver (Ag) nanoparticles in the direction of laser polarization is achieved by utilizing femtosecond laser irradiation in air at laser fluence ranging from ∼2 mJ/cm{sup 2} to ∼14 mJ/cm{sup 2}. This directional ablation is attributed to localized surface plasmon induced localized electric field enhancement. Scanning electron microscopy observations of the irradiated particles in different gases and at different pressures indicate that the ablation is further enhanced by oxygen in the air. This may be due to the external heating via the reactions of its dissociation product, atomic oxygen, with the surface of Ag particles, while the ablated Ag is not oxidized. Further experimental observations show that the ablated material re-deposits near the irradiated particles and results in the extension of the particles in laser polarization direction, facilitating the interconnection of two well-separated nanoparticles.

  19. Multiterawatt femtosecond laser system with kilohertz pulse repetition rate

    NASA Astrophysics Data System (ADS)

    Petrov, V. V.; Pestryakov, E. V.; Laptev, A. V.; Petrov, V. A.; Kuptsov, G. V.; Trunov, V. I.; Frolov, S. A.

    2014-05-01

    The basic principles, layout and components are presented for a multiterawatt femtosecond laser system with a kilohertz pulse repetition rate f, based on their parametric amplification and laser amplification of picosecond radiation that pumps the stages of the parametric amplifier. The results of calculations for a step-by-step increase in the output power from the LBO crystal parametric amplifier channel up to the multiterawatt level are presented. By using the developed components in the pump channel of the laser system, the parameters of the regenerative amplifier with the output energy ~1 mJ at the wavelength 1030 nm and with f = 1 kHz are experimentally studied. The optical scheme of the diode-pumped multipass cryogenic Yb:Y2O3 laser ceramic amplifier is developed and its characteristics are determined that provide the output energy within the range 0.25 - 0.35 J.

  20. Nanostructuring of ITO thin films through femtosecond laser ablation

    NASA Astrophysics Data System (ADS)

    Sahin, Ramazan; Kabacelik, Ismail

    2016-04-01

    Due to reduced thermal effects, tightly focused femtosecond laser beams can yield submicron resolution with minimal side effects. In laser direct writing applications, diffraction-free nature of the Bessel beams relaxes alignment of the sample and shortens the production time. Micron-sized central spots and long depth of focused beams can be simultaneously produced. We apply fs Bessel beam single-pulse ablation method to transparent conductive oxide films. We use laser of 1030 nm wavelength and two different axicons (base angles are 25° and 40°). Fabricated structures are characterized by optical microscope, atomic force microscope and scanning electron microscope. Laser beam shaping and virtues of non-diffracted Bessel beams provide periodic structures for scribing in the solar cells or high-resolution displays and reduce the process time.

  1. Femtosecond laser micromachining for the realization of fully integrated photonic and microfluidic devices

    NASA Astrophysics Data System (ADS)

    Eaton, S. M.; Osellame, R.; Ramponi, R.

    2015-02-01

    Femtosecond laser microprocessing is a direct, maskless fabrication technique that has attracted much attention in the past 10 years due to its unprecedented versatility in the 3D patterning of transparent materials. Two common modalities of femtosecond laser microfabrication include buried optical waveguide writing and surface laser ablation, which have been applied to a wide range of transparent substrates including glasses, polymers and crystals. In two photon polymerization, a third modality of femtosecond laser fabrication, focused femtosecond laser pulses drive photopolymerization in photoresists, enabling the writing of complex 3D structures with submicrometer resolution. In this paper, we discuss several microdevices realized by these diverse modalities of femtosecond laser microfabrication, for applications in microfluidics, sensing and quantum information.

  2. Correlation between anterior chamber characteristics and laser flare photometry immediately after femtosecond laser treatment before phacoemulsification.

    PubMed

    Pahlitzsch, M; Torun, N; Pahlitzsch, M L; Klamann, M K J; Gonnermann, J; Bertelmann, E; Pahlitzsch, T

    2016-08-01

    PurposeTo assess the anterior chamber (AC) characteristics and its correlation to laser flare photometry immediately after femtosecond laser-assisted capsulotomy and photodisruption.Patients and methodsThe study included 97 cataract eyes (n=97, mean age 68.6 years) undergoing femtosecond laser-assisted cataract surgery (FLACS). Three cohorts were analysed relating to the flare photometry directly post femtosecond laser treatment (flare <100 n=28, 69.6±7 years; flare 100-249 n=47, 67.7±8 years; flare >249 photon counts per ms cohort n=22, 68.5±10 years). Flare photometry (KOWA FM-700), corneal topography (Oculus Pentacam, Germany: AC depth, volume, angle, pachymetry), axial length, pupil diameter, and endothelial cells were assessed before FLACS, immediately after femtosecond laser treatment and 1 day postoperative (LenSx Alcon, USA). Statistical data were analysed by SPSS v19.0, Inc.ResultsThe AC depth, AC volume, AC angle, central and thinnest corneal thickness showed a significant difference between flare <100 vs flare 100-249 10 min post femtosecond laser procedure (P=0.002, P=0.023, P=0.007, P=0.003, P=0.011, respectively). The AC depth, AC volume, and AC angle were significantly larger (P=0.001, P=0.007, P=0.003, respectively) in the flare <100 vs flare >249 cohort 10 min post femtosecond laser treatment.ConclusionsA flat AC, low AC volume, and a narrow AC angle were parameters associated with higher intraocular inflammation. These criteria could be used for patient selection in FLACS to reduce postoperative intraocular inflammation. PMID:27229702

  3. Femtosecond laser ablation of gold interdigitated electrodes for electronic tongues

    NASA Astrophysics Data System (ADS)

    Manzoli, Alexandra; de Almeida, Gustavo F. B.; Filho, José A.; Mattoso, Luiz H. C.; Riul, Antonio; Mendonca, Cleber R.; Correa, Daniel S.

    2015-06-01

    Electronic tongue (e-tongue) sensors based on impedance spectroscopy have emerged as a potential technology to evaluate the quality and chemical composition of food, beverages, and pharmaceuticals. E-tongues usually employ transducers based on metal interdigitated electrodes (IDEs) coated with a thin layer of an active material, which is capable of interacting chemically with several types of analytes. IDEs are usually produced by photolithographic methods, which are time-consuming and costly, therefore, new fabrication technologies are required to make it more affordable. Here, we employed femtosecond laser ablation with pulse duration of 50 fs to microfabricate gold IDEs having finger width from 2.3 μm up to 3.2 μm. The parameters used in the laser ablation technique, such as light intensity, scan speed and beam spot size have been optimized to achieve uniform IDEs, which were characterized by optical and scanning electron microscopy. The electrical properties of gold IDEs fabricated by laser ablation were evaluated by impedance spectroscopy, and compared to those produced by conventional photolithography. The results show that femtosecond laser ablation is a promising alternative to conventional photolithography for fabricating metal IDEs for e-tongue systems.

  4. Fabrication of optical cavities with femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Lin, Jintian; Song, Jiangxin; Tang, Jialei; Fang, Wei; Sugioka, Koji; Cheng, Ya

    2014-03-01

    We report on fabrication of three-dimensional (3D) high-quality (Q) whispering-gallery-mode microcavities by femtosecond laser micromachining. The main fabrication procedures include the formation of on-chip freestanding microdisk through selective material removal by femtosecond laser pulses, followed by surface smoothing processes (CO2 laser reflow for amorphous glass and focused ion beam (FIB) sidewall milling for crystalline materials) to improve the Q factors. Fused silica microcavities with 3D geometries are demonstrated with Q factors exceeding 106. A microcavity laser based on Nd:glass has been fabricated, showing a threshold as low as 69μW via free space continuous-wave optical excitation at the room temperature. CaF2 crystalline microcavities with Q factor of ~4.2×104 have also been demonstrated. This technique allows us to fabricate 3D high-Q microcavities in various transparent materials such as glass and crystals, which will benefit a broad spectrum of applications such as nonlinear optics, quantum optics, and bio-sensing.

  5. Focal spot analysis of radially polarized femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Sun, Wenchao; Hu, Wenhua; Qi, Junli; Wang, Weiming; Liao, Jiali; Yi, Wenjun; Jia, Hui; Li, Xiujian

    2014-09-01

    When radially polarized light beams focus through high numerical-aperture lens, there will be a very strong longitudinal component of the light field near the focus. And, under the condition of certain system parameters, they can shape a spot which is over the focusing spot of the diffraction limit, which are the superiorities that linearly polarized light and circularly polarized light do not have. Besides, what we have found in the experiment is that radially polarized femtosecond laser pulses own the same superiorities, which provides the basis for using the focusing characteristics of radially polarized light beams under the condition of shorter and more powerful laser pulses. So far, although people have studied a lot on radially polarized light beams, this kind of light beams' focusing characters are rarely researched. What is worse, most research of its focusing characters still stays in the stage of theoretical simulation,and it seems that none of people have really studied it by the way of experiments. This article is precisely based on this. On the basis of predecessors' a lot of theoretical research, the article pays more attention on analyzing radially polarized light beams' focusing character through experiments. What's more, the article, based on femtosecond laser pulses, compares the differences of the focusing nature among linearly polarized light, circularly polarized light and radially polarized light. And it gets the conclusion that radially polarized femtosecond laser pulses have better focusing character in longitudinal light field, confirming the feasibility that radially polarized light beams can be used in the fields of pulling, catching, and accelerating particles, metal cutting and high-density storage.

  6. Electrochemical behavior of nano and femtosecond laser textured titanium alloy for implant surface modification.

    PubMed

    Jeong, Yong-Hoon; Kim, Won-Gi; Choe, Han-Cheol

    2011-02-01

    In this study, the electrochemical behavior of nano and femtosecond laser textured titanium alloy for implant surface modification has been researched using the potentiostat equipment. Cp-Ti and Ti-6Al-4V alloy, located on X-Y motorized stage, were irradiated using femtosecond laser. The corrosion properties were examined by a potentiodynamic and AC impedance test. PMID:21456241

  7. Femtosecond laser heat affected zones profiled in Co/Si multilayer thin films

    SciTech Connect

    Picard, Yoosuf N.; Yalisove, Steven M.

    2008-01-07

    In this letter, we describe an approach for assessing collateral thermal damage resulting from high intensity, femtosecond laser irradiation. Polycrystalline Co thin films deposited on Si (100) substrates and buried under an amorphous Si film were prepared for plan-view transmission electron microscopy (TEM) prior to laser irradiation by femtosecond laser pulses. A heat affected zone (HAZ) resulting from single pulse irradiation at a fluence of 0.9 J/cm{sup 2} was determined by TEM imaging and point-wise selected area diffraction. The spatially Gaussian laser pulse generated a HAZ extending up to 3 {mu}m radially from the femtosecond laser irradiated region.

  8. Femtosecond laser ablation elemental mass spectrometry.

    PubMed

    Hergenröder, Roland; Samek, Ota; Hommes, Vanja

    2006-01-01

    Laser ablation mass spectrometry (LA-MS) has always been an interesting method for the elemental analysis of solid samples. Chemical analysis with a laser requires small amounts of material. Depending on the analytical detection system, subpicogram quantities may be sufficient. In addition, a focused laser beam permits the spatial characterization of heterogeneity in solid samples typically with micrometer resolution in terms of lateral and depth dimensions. With the advent of high-energy, ultra-short pulse lasers, new possibilities arise. The task of this review is to discuss the principle differences between the ablation process of short (>1 ps) and ultra-short (<1 ps) pulses. Based on the timescales and the energy balance of the process that underlies an ablation event, it will be shown that ultra-short pulses are less thermal and cause less collateral damages than longer pulses. The confinement of the pulse energy to the focal region guarantees a better spatial resolution in all dimensions and improves the analytical figures of merit (e.g., fractionation). Applications that demonstrate these features and that will be presented are in-depth profiling of multi-layer samples and the elemental analysis of biological materials. PMID:16477613

  9. Femtosecond laser processing of photovoltaic and transparent materials

    NASA Astrophysics Data System (ADS)

    Ahn, Sanghoon

    The photovoltaic semiconducting and transparent dielectric materials are of high interest in current industry. Femtosecond laser processing can be an effective technique to fabricate such materials since non-linear photochemical mechanisms predominantly occur. In this series of studies, femtosecond (fs) laser processing techniques that include laser drilling on Si wafer, laser scribing on CIGS thin film, laser ablation on Lithium Niobate (LN) crystal, and fabrication of 3D structures in fused silica were studied. The fs laser drilling on Si wafer was performed to fabricate via holes for wrap-through PV devices. For reduction of the number of shots in fs laser drilling process, self-action of laser light in the air was initiated. To understand physical phenomena during laser drilling, scanning electron microscopy (SEM), emission, and shadowgraph images were studied. The result indicated the presence of two mechanisms that include fabrication by self-guided beam and wall-guided beam. Based on our study, we could fabricate ~16 micrometer circular-shaped via holes with ~200 laser pulses on 160-170 micrometer thick c- and mc-Si wafer. For the fs laser scribing on ink jet printed CIGS thin film solar cell, the effect of various parameters that include pulse accumulation, wavelength, pulse energy, and overlapping were elucidated. In our processing regime, the effect of wavelength could be diminished due to compensation between beam size, pulse accumulation, energy fluence, and the absorption coefficient. On the other hand, for high PRF fs laser processing, pulse accumulation effect cannot be ignored, while it can be negligible in low PRF fs laser processing. The result indicated the presence of a critical energy fluence for initiating delamination of CIGS layer. To avoid delamination and fabricate fine isolation lines, the overlapping method can be applied. With this method, ~1 micrometer width isolation lines were fabricated. The fs laser ablation on LN wafer was studied

  10. Ultraprecise medical applications with ultrafast lasers: corneal surgery with femtosecond lasers

    NASA Astrophysics Data System (ADS)

    Loesel, Frieder H.; Kurtz, Ron M.; Horvath, Christopher; Sayegh, Samir I.; Mourou, Gerard A.; Bille, Josef F.; Juhasz, Tibor

    1999-02-01

    We investigated refractive corneal surgery in vivo and in vitro by intrastromal photodisruption using a compact ultrafast femtosecond laser system. Ultrashort-pulsed lasers operating in the femtosecond time regime are associated with significantly smaller and deterministic threshold energies for photodisruption, as well as reduced shock waves and smaller cavitation bubbles than the nanosecond or picosecond lasers. Our reliable all-solid-state laser system was specifically designed for real world medical applications. By scanning the 5 micron focus spot of the laser below the corneal surface, the overlapping small ablation volumes of single pulses resulted in contiguous tissue cutting and vaporization. Pulse energies were typically in the order of a few microjoules. Combination of different scanning patterns enabled us to perform corneal flap cutting, femtosecond-LASIK, and femtosecond intrastromal keratectomy in porcine, rabbit, and primate eyes. The cuts proved to be highly precise and possessed superior dissection and surface quality. Preliminary studies show consistent refractive changes in the in vivo studies. We conclude that the technology is capable to perform a variety of corneal refractive procedures at high precision, offering advantages over current mechanical and laser devices and enabling entirely new approaches for refractive surgery.

  11. Organic random laser in an optofluidic chip fabricated by femtosecond laser

    NASA Astrophysics Data System (ADS)

    Vishnubhatla, Krishna Chaitanya; Osellame, Roberto; Lanzani, Guglielmo; Ramponi, Roberta; Virgili, Tersilla

    2010-02-01

    Femtosecond laser based micromachining technologies have the inherent capability of producing elements in 3D. Their ability of rapid prototyping can be exploited to develop novel Optofluidics devices. Microfluidic channels were fabricated and integrated with optical waveguides using a single femtosecond laser. Optically pumping the microchannel filled with polyfluorene solution and by dispersing nanoparticles in the solution, random lasing in the microchannel is obtained. We demonstrate a novel approach to organic photonic devices, where the unique properties of a conjugated polymer in solution are exploited in a microfluidic configuration in order to produce easy-to-integrate photonic devices.

  12. Measurement of acceleration in femtosecond laser-plasmas

    SciTech Connect

    Haessner, R.; Theobald, W.; Niedermeier, S.; Michelmann, K.; Feurer, T.; Schillinger, H.; Sauerbrey, R.

    1998-02-20

    Accelerations up to 4x10{sup 19} m/s{sup 2} are measured in femtosecond laser-produced plasmas at intensities of 10{sup 18} W/cm{sup 2} using the Frequency Resolved Optical Gating (FROG) technique. A high density plasma is formed by focusing an ultrashort unchirped laser pulse on a plane carbon target and part of the reflected pulse is eventually detected by a FROG autocorrelator. Radiation pressure and thermal pressure accelerate the plasma which causes a chirp in the reflected laser pulse. The retrieved phase and amplitude information reveal that the plasma motion is dominated by the large light pressure which pushes the plasma into the target. This is supported by theoretical estimates and by the results of independently measured time integrated spectra of the reflected pulse.

  13. Femtosecond Laser Patterning of the Biopolymer Chitosan for Biofilm Formation.

    PubMed

    Estevam-Alves, Regina; Ferreira, Paulo Henrique Dias; Coatrini, Andrey C; Oliveira, Osvaldo N; Fontana, Carla Raquel; Mendonca, Cleber Renato

    2016-01-01

    Controlling microbial growth is crucial for many biomedical, pharmaceutical and food industry applications. In this paper, we used a femtosecond laser to microstructure the surface of chitosan, a biocompatible polymer that has been explored for applications ranging from antimicrobial action to drug delivery. The influence of energy density on the features produced on chitosan was investigated by optical and atomic force microscopies. An increase in the hydrophilic character of the chitosan surface was attained upon laser micromachining. Patterned chitosan films were used to observe Staphylococcus aureus (ATCC 25923) biofilm formation, revealing an increase in the biofilm formation in the structured regions. Our results indicate that fs-laser micromachining is an attractive option to pattern biocompatible surfaces, and to investigate basic aspects of the relationship between surface topography and bacterial adhesion. PMID:27548153

  14. Femtosecond laser-drilled capillary integrated into a microfluidic device

    SciTech Connect

    Kim, Tyson N.; Campbell, Kyle; Groisman, Alex; Kleinfeld, David; Schaffer, Chris B.

    2005-05-16

    Recent growth in microfluidic technology is, to a large extent, driven by soft lithography, a high-throughput fabrication technique where polymer materials, such as poly(dimethyl) siloxane (PDMS), are molded to form microscopic channel networks. Nevertheless, the channel architectures that can be obtained by molding are limited. We address this limitation by using femtosecond laser micromachining to add unmoldable features to the microfluidic devices. We apply laser ablation to drill microcapillaries, with diameters as small as 0.5 {mu}m and aspect ratios as high as 800:1, in the walls of molded PDMS channels. Finally, we use a laser-drilled microcapillary to trap a polystyrene bead by suction and hold it against a shear flow.

  15. Nanoscale patterning of graphene through femtosecond laser ablation

    SciTech Connect

    Sahin, R.; Akturk, S.; Simsek, E.

    2014-02-03

    We report on nanometer-scale patterning of single layer graphene on SiO{sub 2}/Si substrate through femtosecond laser ablation. The pulse fluence is adjusted around the single-pulse ablation threshold of graphene. It is shown that, even though both SiO{sub 2} and Si have more absorption in the linear regime compared to graphene, the substrate can be kept intact during the process. This is achieved by scanning the sample under laser illumination at speeds yielding a few numbers of overlapping pulses at a certain point, thereby effectively shielding the substrate. By adjusting laser fluence and translation speed, 400 nm wide ablation channels could be achieved over 100 μm length. Raster scanning of the sample yields well-ordered periodic structures, provided that sufficient gap is left between channels. Nanoscale patterning of graphene without substrate damage is verified with Scanning Electron Microscope and Raman studies.

  16. Reinforced direct bonding of optical materials by femtosecond laser welding.

    PubMed

    Hélie, David; Bégin, Michael; Lacroix, Fabrice; Vallée, Réal

    2012-04-20

    A process for reinforcing a direct bond between optical materials using femtosecond laser welding is presented. As a side benefit, the optical transmission properties of the joined components are shown not to be altered by the joining process. The joints exhibits higher shear breakage loads, yielding a maximum measured joint strength of 5.25 MPa for an applied load of 75 kg in fused silica. The laser sealing of direct bonds between dissimilar materials improves their resistance to thermal shocks. Direct bonds sealed by a circular weld seam can withstand thermal shocks at temperatures at least twice as great as nonreinforced direct bonds. The combination of ultrashort laser welding and direct bonding provides an innovative joining method that benefits from the advantages of both contributing physical processes. PMID:22534922

  17. Femtosecond laser pulse train interaction with dielectric materials

    NASA Astrophysics Data System (ADS)

    Dematteo Caulier, O.; Mishchik, K.; Chimier, B.; Skupin, S.; Bourgeade, A.; Javaux Léger, C.; Kling, R.; Hönninger, C.; Lopez, J.; Tikhonchuk, V.; Duchateau, G.

    2015-11-01

    The interaction of trains of femtosecond microjoule laser pulses with dielectric materials by means of a multi-scale model is investigated. Theoretical predictions are directly confronted with experimental observations in soda-lime glass. It is shown that due to the low heat conductivity, a significant fraction of the laser energy can be accumulated in the absorption region. Depending on the pulse repetition rate, the material can be heated to high temperatures even though the single pulse energy is too low to induce a significant material modification. Regions heated above the glass transition temperature in the simulations correspond very well to zones of permanent material modifications observed in the experiments. It turns out that pulse-to-pulse variations of the laser absorption are negligible and of minor influence to permanent material modifications.

  18. Femtosecond Laser Patterning of the Biopolymer Chitosan for Biofilm Formation

    PubMed Central

    Estevam-Alves, Regina; Ferreira, Paulo Henrique Dias; Coatrini, Andrey C.; Oliveira, Osvaldo N.; Fontana, Carla Raquel; Mendonca, Cleber Renato

    2016-01-01

    Controlling microbial growth is crucial for many biomedical, pharmaceutical and food industry applications. In this paper, we used a femtosecond laser to microstructure the surface of chitosan, a biocompatible polymer that has been explored for applications ranging from antimicrobial action to drug delivery. The influence of energy density on the features produced on chitosan was investigated by optical and atomic force microscopies. An increase in the hydrophilic character of the chitosan surface was attained upon laser micromachining. Patterned chitosan films were used to observe Staphylococcus aureus (ATCC 25923) biofilm formation, revealing an increase in the biofilm formation in the structured regions. Our results indicate that fs-laser micromachining is an attractive option to pattern biocompatible surfaces, and to investigate basic aspects of the relationship between surface topography and bacterial adhesion. PMID:27548153

  19. Femtosecond pulsed laser deposition of biological and biocompatible thin layers

    NASA Astrophysics Data System (ADS)

    Hopp, B.; Smausz, T.; Kecskeméti, G.; Klini, A.; Bor, Zs.

    2007-07-01

    In our study we investigate and report the femtosecond pulsed laser deposition of biological and biocompatible materials. Teflon, polyhydroxybutyrate, polyglycolic-acid, pepsin and tooth in the form of pressed pellets were used as target materials. Thin layers were deposited using pulses from a femtosecond KrF excimer laser system (FWHM = 450 fs, λ = 248 nm, f = 10 Hz) at different fluences: 0.6, 0.9, 1.6, 2.2, 2.8 and 3.5 J/cm 2, respectively. Potassium bromide were used as substrates for diagnostic measurements of the films on a FTIR spectrometer. The pressure in the PLD chamber was 1 × 10 -3 Pa, and in the case of tooth and Teflon the substrates were heated at 250 °C. Under the optimized conditions the chemical structure of the deposited materials seemed to be largely preserved as evidenced by the corresponding IR spectra. The polyglycolic-acid films showed new spectral features indicating considerable morphological changes during PLD. Surface structure and thickness of the layers deposited on Si substrates were examined by an atomic force microscopy (AFM) and a surface profilometer. An empirical model has been elaborated for the description of the femtosecond PLD process. According to this the laser photons are absorbed in the surface layer of target resulting in chemical dissociation of molecules. The fast decomposition causes explosion-like gas expansion generating recoil forces which can tear off and accelerate solid particles. These grains containing target molecules without any chemical damages are ejected from the target and deposited onto the substrate forming a thin layer.

  20. Polycrystalline VO2 thin films via femtosecond laser processing of amorphous VO x

    NASA Astrophysics Data System (ADS)

    Charipar, N. A.; Kim, H.; Breckenfeld, E.; Charipar, K. M.; Mathews, S. A.; Piqué, A.

    2016-05-01

    Femtosecond laser processing of pulsed laser-deposited amorphous vanadium oxide thin films was investigated. Polycrystalline VO2 thin films were achieved by femtosecond laser processing in air at room temperature. The electrical transport properties, crystal structure, surface morphology, and optical properties were characterized. The laser-processed films exhibited a metal-insulator phase transition characteristic of VO2, thus presenting a pathway for the growth of crystalline vanadium dioxide films on low-temperature substrates.

  1. Femtosecond laser patterning of biological materials

    NASA Astrophysics Data System (ADS)

    Grigoropoulos, Costas P.; Jeon, Hojeong; Hidai, Hirofumi; Hwang, David J.

    2011-03-01

    This paper aims at presenting a review of work at the Laser Thermal Laboratory on the microscopic laser modification of biological materials using ultrafast laser pulses. We have devised a new method for fabricating high aspect ratio patterns of varying height by using two-photon polymerization process in order to study contact guidance and directed growth of biological cells. Studies using NIH-3T3 and MDCK cells indicate that cell morphology on fiber scaffolds is influenced by the pattern of actin microfilament bundles. Cells experienced different strength of contact guidance depending on the ridge height. Cell morphology and motility was investigated on micronscale anisotropic cross patterns and parallel line patterns having different aspect ratios. A significant effect on cell alignment and directionality of migration was observed. Cell morphology and motility were influenced by the aspect ratio of the cross pattern, the grid size, and the ridge height. Cell contractility was examined microscopically in order to measure contractile forces generated by individual cells on self-standing fiber scaffolds.

  2. Ultrasmall Silver Nanopores Fabricated by Femtosecond Laser Pulses

    NASA Astrophysics Data System (ADS)

    Zhao, Jimin; Bian, F.; Tian, Y. C.; Wang, R.; Yang, H. X.; Xu, Hongxing; Meng, Sheng

    2012-02-01

    Ultrasmall nanopores in silver thin films with a diameter of about 2 nm have been fabricated using femtosecond laser ablation in liquid [1]. Ultrafast laser pulse ablation generates highly nonequilibrium excitated states, from which silver thin films emerge and progressively grow with the assistance of capping agent molecules. During this growth process, capping agent molecules are enclaves within the film, leaving individual ultrasmall pores in the thin film. Our first-principles calculations show that the pore size is critically determined by the dimension of the confined molecules. Furthermore, by using smaller capping agent molecules, we were able to fabricate smaller nanopores with 1.6nm diameter. Our approach advances the capability of optical methods in making nanoscale structures with potential applications in areas such as near-field aperture probes, imaging masks, magnetic plasmonic resonances, and biosensing with individual nanopores. [4pt] [1] F. Bian, Y. C. Tian, R. Wang, H. X. Yang, H. X. Xu, Sheng Meng, and Jimin Zhao, Ultrasmall Silver Nanopores Fabricated by Femtosecond Laser Pulses, Nano Lett. 11, 3251--3257 (2011).

  3. Microfabrication of transparent materials using filamented femtosecond laser beams

    NASA Astrophysics Data System (ADS)

    Butkus, S.; Paipulas, D.; Gaižauskas, Eugenijus; KaškelytÄ--, D.; Sirutkaitis, V.

    2014-05-01

    Glass drilling realized with the help of femtosecond lasers attract industrial attention, however, desired tasks may require systems employing high numerical aperture (NA) focusing conditions, low repetition rate lasers and complex fast motion translation stages. Due to the sensitivity of such systems, slight instabilities in parameter values can lead to crack formations, severe fabrication rate decrement and poor quality overall results. A microfabrication system lacking the stated disadvantages was constructed and demonstrated in this report. An f-theta lens was used in combination with a galvanometric scanner, in addition, a water pumping system that enables formation of water films of variable thickness in real time on the samples. Water acts as a medium for filament formation, which in turn decreases the focal spot diameter and increases fluence and axial focal length. This article demonstrates the application of a femtosecond (280fs) laser towards rapid cutting of different transparent materials. Filament formation in water gives rise to strong ablation at the surface of the sample, moreover, the water, surrounding the ablated area, adds increased cooling and protection from cracking. The constructed microfabrication system is capable of drilling holes in thick soda-lime, hardened glasses and sapphire. The fabrication time varies depending on the diameter of the hole and spans from a few to several hundred seconds. Moreover, complex-shape fabrication was demonstrated.

  4. Investigation of diffractive optical element femtosecond laser machining

    NASA Astrophysics Data System (ADS)

    Chabrol, Grégoire R.; Ciceron, Adline; Twardowski, Patrice; Pfeiffer, Pierre; Flury, Manuel; Mermet, Frédéric; Lecler, Sylvain

    2016-06-01

    This paper presents an explorative study on the machining of diffractive optical elements (DOEs) in transparent materials using a femtosecond laser source. A simple form of DOE, a binary phase grating with a period of 20.85 μm (σ = 0.5 μm), a groove depth and width of 0.7 μm (σ = 0.2 μm) and 8.8 μm (σ = 0.5 μm) respectively, was successfully machined in BK7. The topographic characteristics were measured by white light interferometry and scanning electron microscopy (SEM). The processing was carried out on high precision stages with an ultrafast fibre laser (350 fs) emitting a 343 nm pulse focused onto the sample with a stationary microscope objective. A diffracted efficiency of 27%, obtained with a spectro goniometer, was corroborated by the theoretical results obtained by the Fourier modal method (FMM), taking into account the measured topographic values. These encouraging results demonstrate that high-speed femtosecond laser manufacturing of DOE in bulk glasses can be achieved, opening the way to rapid prototyping of multi-layered-DOEs.

  5. Pulse front tilt measurement of femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Dimitrov, Nikolay; Stoyanov, Lyubomir; Stefanov, Ivan; Dreischuh, Alexander; Hansinger, Peter; Paulus, Gerhard G.

    2016-07-01

    In this work we report experimental investigations of an intentionally introduced pulse front tilt on femtosecond laser pulses by using an inverted field correlator/interferometer. A reliable criterion for the precision in aligning (in principle) dispersionless systems for manipulating ultrashort pulses is developed, specifically including cases when the pulse front tilt is a result of a desired spatio-temporal coupling. The results obtained using two low-dispersion diffraction gratings are in good qualitative agreement with the data from a previously developed analytical model and from an independent interferometric measurement.

  6. Femtosecond laser ablation of dentin and enamel: relationship between laser fluence and ablation efficiency

    NASA Astrophysics Data System (ADS)

    Chen, Hu; Liu, Jing; Li, Hong; Ge, Wenqi; Sun, Yuchun; Wang, Yong; Lü, Peijun

    2015-02-01

    The objective was to study the relationship between laser fluence and ablation efficiency of a femtosecond laser with a Gaussian-shaped pulse used to ablate dentin and enamel for prosthodontic tooth preparation. A diode-pumped thin-disk femtosecond laser with wavelength of 1025 nm and pulse width of 400 fs was used for the ablation of dentin and enamel. The laser spot was guided in a line on the dentin and enamel surfaces to form a groove-shaped ablation zone under a series of laser pulse energies. The width and volume of the ablated line were measured under a three-dimensional confocal microscope to calculate the ablation efficiency. Ablation efficiency for dentin reached a maximum value of 0.020 mm3/J when the laser fluence was set at 6.51 J/cm2. For enamel, the maximum ablation efficiency was 0.009 mm3/J at a fluence of 7.59 J/cm2. Ablation efficiency of the femtosecond laser on dentin and enamel is closely related to the laser fluence and may reach a maximum when the laser fluence is set to an appropriate value.

  7. Femtosecond laser ablation properties of transparent materials: impact of the laser process parameters on the machining throughput

    NASA Astrophysics Data System (ADS)

    Matylitsky, V. V.; Hendricks, F.; Aus der Au, J.

    2013-03-01

    High average power, high repetition rate femtosecond lasers with μJ pulse energies are increasingly used for bio-medical and material processing applications. With the introduction of femtosecond laser systems such as the SpiritTM platform developed by High Q Lasers and Spectra-Physics, micro-processing of solid targets with femtosecond laser pulses have obtained new perspectives for industrial applications [1]. The unique advantage of material processing with subpicosecond lasers is efficient, fast and localized energy deposition, which leads to high ablation efficiency and accuracy in nearly all kinds of solid materials. The study on the impact of the laser processing parameters on the removal rate for transparent substrate using femtosecond laser pulses will be presented. In particular, examples of micro-processing of poly-L-lactic acid (PLLA) - bio-degradable polyester and XensationTM glass (Schott) machined with SpiritTM ultrafast laser will be shown.

  8. High repetition rate femtosecond laser forming sub-10 µm diameter interconnection vias

    NASA Astrophysics Data System (ADS)

    Tan, B; Panchatsharam, S; Venkatakrishnan, K

    2009-03-01

    Laser ablative microvia formation has been widely accepted as an effective manufacturing method for interconnect via formation. Current conventional nanosecond laser microvia formation has reached its limit in terms of minimum via diameter and machining quality. Femtosecond laser has been investigated intensively for its superior machining quality and capability of producing much smaller features. However, the traditional femtosecond laser has very low power and is thus unable to meet the throughput requirement. In this paper we report ablative microvia formation using femtosecond lasers at megahertz repetition rates. Laser ablation was demonstrated for the first time for sub-10 µm interconnection via drilling at a throughput of 10 000 vias per second. A systematic study of the influence of a high repetition rate in femtosecond laser micromachining of silicon was carried out. The experiments were performed using an Yb-doped fibre amplified/oscillator laser with 1030 nm wavelength in an air environment. The effects of a high repetition rate on microvia formation were observed at ~300 fs for silicon substrates. Laser parameters along with threshold energy, via diameter, ablation depth, ablation rate and via quality were studied in detail to accentuate the need of femtosecond lasers for forming sub-10 µm diameter microvias. The experimental results show that femtosecond laser pulses with high repetition rates show unequivocally the advantages of short-pulse laser ablation for high-precision applications in micrometre-scale dimensions.

  9. Femtosecond laser damage in dielectric coatings

    NASA Astrophysics Data System (ADS)

    Bonse, Joern; Baudach, Steffen; Krueger, Joerg; Kautek, Wolfgang; Starke, Kai; Gross, Tobias; Ristau, Detlev; Rudolph, Wolfgang G.; Jasapara, Jayesh C.; Welsch, Eberhard

    2001-04-01

    Multi-shot investigations of Ti:sapphire laser (wavelength (lambda) approximately equals 800 nm) induced damage were performed in three different laboratories (BAM, Berlin; LZH, Hannover; UNM, Albuquerque). The ablation behavior of a high reflecting mirror consisting of alternating (lambda) /4- layers of Ta2O5 and SiO2 was studied. Fused silica served as substrate. The influence of the pulse duration ((tau) equals 13 - 130 fs), the pulse number (30 - (infinity) ) and the repetition rate (10 Hz - 100 MHz) on the damage threshold will be discussed.

  10. OCT-aided femtosecond laser micromachining device

    NASA Astrophysics Data System (ADS)

    Massow, Ole; Jackstadt, Michael; Wisweh, Henning; Will, Fabian; Lubatschowski, Holger

    2009-02-01

    Fs-lasers are widely used for microsurgery and micromachining. Due to nonlinear interaction of ultrashort pulses with tissue or matter precisions of a few μm can be achieved. But particularly in the field of surgery this precision can not be obtained as the devices for diagnostics and treatment have to be changed due to separate systems. We show a combined system of a fs-laser and a Fourier-Domain optical coherence tomography (FD-OCT) enabling to cut and image the region of interest alternately. The FD-OCT offers non-invasive imaging at an axial resolution of 6, 2 μm and a transverse resolution of 3 μm in air which is comparable to the interaction zone of the fslaser-pulses. OCT-aided subsurface cutting is successfully demonstrated on biological ex-vito samples of porcine cornea and larynx. Furthermore it appeared that in situ OCT imaging enables to monitor cuts produced with pulse energies close to the energy threshold. In conclusion, this setup demonstrates the potential of a system combining cutting and OCT imaging within the same optical setup without the need of changing devices.

  11. Pressure effects on the femtosecond laser filamentation

    NASA Astrophysics Data System (ADS)

    Qi, Xiexing; Ma, Cunliang; Lin, Wenbin

    2016-01-01

    We investigate the pressure effects on the propagation of the laser pulse with wavelength of 800 nm by numerical simulations. We consider the effects on the on-axis intensity, the beam radius and the energy of the filament, as well as the on-axis density of plasma. Numerical results show that when the pressures increase, the length, radius and energy of the light filament become shorter, narrower and lower, respectively. Moreover, we find that the length and the radius of filament are approximately inversely proportional to the pressure and the square root of pressure, respectively, and the pulse with shorter duration is easier to be affected by the pressure. We also obtain the conclusion that the plasma is not necessary to generate the filament in gases in various pressures, as stated by Béjot et al. [1] for the case of standard atmosphere pressure.

  12. Femtosecond laser for glaucoma treatment: the comparison between simulation and experimentation results on ocular tissue removal

    NASA Astrophysics Data System (ADS)

    Hou, Dong Xia; Ngoi, Bryan K. A.; Hoh, Sek Tien; Koh, Lee Huat K.; Deng, Yuan Zi

    2005-04-01

    In ophthalmology, the use of femtosecond lasers is receiving more attention than ever due to its extremely high intensity and ultra short pulse duration. It opens the highly beneficial possibilities for minimized side effects during surgery process, and one of the specific areas is laser surgery in glaucoma treatment. However, the sophisticated femtosecond laser-ocular tissue interaction mechanism hampers the clinical application of femtosecond laser to treat glaucoma. The potential contribution in this work lies in the fact, that this is the first time a modified moving breakdown theory is applied, which is appropriate for femtosecond time scale, to analyze femtosecond laser-ocular tissue interaction mechanism. Based on this theory, energy deposition and corresponding thermal increase are studied by both simulation and experimentation. A simulation model was developed using Matlab software, and the simulation result was validated through in-vitro laser-tissue interaction experiment using pig iris. By comparing the theoretical and experimental results, it is shown that femtosecond laser can obtain determined ocular tissue removal, and the thermal damage is evidently reduced. This result provides a promising potential for femtosecond laser in glaucoma treatment.

  13. Curved Yb:YAG waveguide lasers, fabricated by femtosecond laser inscription.

    PubMed

    Calmano, Thomas; Paschke, Anna-Greta; Müller, Sebastian; Kränkel, Christian; Huber, Günter

    2013-10-21

    Straight and s-curve Yb(7%):YAG waveguides have been fabricated with the femtosecond laser writing technique. By employing a novel writing scheme an increase of the refractive index change could be achieved in comparison to waveguides written with the standard procedure. Straight waveguides, fabricated with this scheme, enabled highly efficient Ti:sapphire laser pumped waveguide lasers with slope efficiencies of 79% and output powers of more than 1 W. With slope efficiencies from 50% to 60% for the curved waveguide lasers with radii of curvature of R ≥ 20 mm the possibility of fs-laser written complex optical devices is demonstrated. PMID:24150389

  14. Dry eye associated with laser in situ keratomileusis: Mechanical microkeratome versus femtosecond laser

    PubMed Central

    Salomão, Marcella Q.; Ambrósio, Renato; Wilson, Steven E.

    2014-01-01

    Purpose To compare the incidence of laser in situ keratomileusis (LASIK)–associated dry eye and the need for postoperative cyclosporine A treatment after flap creation with a femtosecond laser or a mechanical microkeratome. Setting Cole Eye Institute, Cleveland, Ohio, USA. Methods Eyes were randomized to flap creation with an IntraLase femtosecond laser (30 or 60 kHz) or a Hansatome microkeratome. No patient had signs, symptoms, or treatment of dry eye preoperatively. Flap thickness was determined by intraoperative ultrasonic pachymetry. Slitlamp assessments of the cornea and need for postoperative dry-eye treatment were evaluated preoperatively and 1 month postoperatively. Results The flap was created with the femtosecond laser in 113 eyes and with the microkeratome in 70 eyes. The difference in mean central flap thickness between the femtosecond group (111 μm ± 14 [SD]) and the microkeratome group (131 ± 25 μm) was statistically significant (P<.001). The incidence of LASIK-associated dry eye was statistically significantly higher in the microkeratome group (46%) than in the femtosecond group (8%) (P<.0001), as was the need for postoperative cyclosporine A treatment (24% and 7%, respectively) (P<.01). In the microkeratome group, there was no correlation between thick flaps and a higher incidence of LASIK-induced dry eye. Conclusions Eyes with femtosecond flaps had a lower incidence of LASIK-associated dry eye and required less treatment for the disorder. In addition to neurotrophic effects from corneal nerve cutting, other factors may be important because no correlation was found between flap thickness (or ablation depth) and the incidence of LASIK-induced dry eye. PMID:19781472

  15. Picosecond and femtosecond laser ablation of hard tissues

    NASA Astrophysics Data System (ADS)

    Serafetinides, Alexander A.; Makropoulou, Mersini I.; Kar, Ajoy K.; Khabbaz, Marouan

    1996-12-01

    In this study, the interaction of picosecond and femtosecond pulsed laser radiation with human dental tissue was investigated experimentally, as this unexplored field is expected to be a potential alternative in powerful laser processing of biomedical structures. Dentin ablation rate experiments were performed by using teeth sections of different thickness. Dental tissue samples were irradiated in air with i) a regenerative amplifier laser at 1064 nm, pulse duration 110 ps, ii) the second harmonic laser at 532 nm, pulse duration 100 ps, and iii) a picosecond tunable dye amplifier at 595 nm, pulse width 800 fs. In all the experiments the pulse repetition rate was 10 Hz. The ablation rate per pulse at different energy fluence settings was calculated by measuring the time needed for the perforation of the whole dental sample thickness. Short laser pulses can confine thermal energy within the optical zone, which maximizes photothermal and photomechanical mechanisms of interaction. Tissue ablation rates were found to be comparable to or better than other nanosecond lasers, and left smooth surfaces, free of thermal damage.

  16. Femtosecond laser ablation of polytetrafluoroethylene (Teflon) in ambient air

    NASA Astrophysics Data System (ADS)

    Wang, Z. B.; Hong, M. H.; Lu, Y. F.; Wu, D. J.; Lan, B.; Chong, T. C.

    2003-05-01

    Teflon, polytetrafluorethylene (PTFE), is an important material in bioscience and medical application due to its special characteristics (bio-compatible, nonflammable, antiadhesive, and heat resistant). The advantages of ultrashort laser processing of Teflon include a minimal thermal penetration region and low processing temperatures, precision removal of material, and good-quality feature definition. In this paper, laser processing of PTFE in ambient air by a Ti:sapphire femtosecond laser (780 nm, 110 fs) is investigated. It is found that the pulse number on each irradiated surface area must be large enough for a clear edge definition and the ablated depth increases with the pulse number. The air ionization effect at high laser fluences not only degrades the ablated structures quality but also reduces the ablation efficiency. High quality microstructures are demonstrated with controlling laser fluence below a critical fluence to exclude the air ionization effect. The ablated microstructures show strong adhesion property to liquids and clear edges that are suitable for bio-implantation applications. Theoretical calculation is used to analyze the evolution of the ablated width and depth at various laser fluences.

  17. Interaction of femtosecond laser pulses with tempera paints

    NASA Astrophysics Data System (ADS)

    Gaspard, Solenne; Oujja, Mohamed; Moreno, Pablo; Méndez, Cruz; García, Ana; Domingo, Concepción; Castillejo, Marta

    2008-12-01

    For the implementation of femtosecond (fs) laser cleaning methodologies of light-sensitive substrates as those encountered in artistic paintings, the interaction between fs laser pulses and painting components has to be well characterized. In this work, the modifications induced by fs laser irradiation of paints are examined in unvarnished aged model temperas. Irradiation at fluences below or above the ablation thresholds by 120 fs pulses at 795 nm from a Ti:Sapphire laser of unpigmented and traditional artist's pigment temperas (cinnabar and chrome yellow) is shown to result in various degrees of discolouration and changes of the laser-induced fluorescence signal. Fourier transform FT-Raman (at 1064 nm) and micro-Raman (at 785 nm) spectroscopic measurements were carried out to assess the changes induced. Noticeable modifications of the Raman bands of the pigments are absent while build-up of extra bands of amorphous carbon (indicative of carbonization or charring) does not take place, in contrast with previous observations upon irradiation with 248 nm, 25 ns pulses. It is concluded that IR fs irradiation provides a high degree of control over the induced modifications, a feature of interest in the design of new laser restoration schemes.

  18. Dynamics of femtosecond laser-induced melting of silver

    SciTech Connect

    Chan Wailun; Averback, Robert S.; Cahill, David G.; Lagoutchev, Alexei

    2008-12-01

    We use optical third-harmonic generation to measure the melting dynamics of silver following femtosecond laser excitation. The dynamics reveals an unusual two-step process that is associated with the extreme electronic temperatures and very short time and length scales. In the first, which lasts a few picoseconds, the electron and phonon systems begin to equilibrate, and a thin surface layer undergoes melting. Heat conduction during this period is strongly suppressed by electron scattering from d-band excitations. In the second stage, the surface region remains above the melting temperature for a surprisingly long time, 20-30 ps, with the melt front propagating into the bulk at a velocity of {approx_equal}350 m s{sup -1}. In this stage, the electron and phonon systems again fall out of equilibrium and conduction of heat away from the surface region is now limited by the weak electron-phonon (e-p) coupling. From our model calculation, we propose that the melt depths in noble metals irradiated by femtosecond lasers are limited to thicknesses on the order of two to three times of the optical-absorption depth of the light.

  19. Metal deep engraving with high average power femtosecond lasers

    NASA Astrophysics Data System (ADS)

    Faucon, M.; Mincuzzi, G.; Morin, F.; Hönninger, C.; Mottay, E.; Kling, R.

    2015-03-01

    Deep engraving of 3D textures is a very demanding process for the creation of master tool e. g molds, forming tools or coining dies. As these masters are uses for reproduction of 3D patterns the materials for the tools are typically hard and brittle and thus difficult to machine. The new generation of industrial femtosecond lasers provides both high accuracy engraving results and high ablation rates at the same time. Operation at pulse energies of typically 40 μJ and repetition rates in the Mhz range the detrimental effect of heat accumulation has to be avoided. Therefore high scanning speeds are required to reduce the pulse overlap below 90%. As a consequence scan speeds in the range of 25-50 m/s a needed, which is beyond the capability of galvo scanners. In this paper we present results using a combination of a polygon scanner with a high average power femtosecond laser and compare this to results with conventional scanners. The effects of pulse energy and scan speed of the head on geometrical accuracy are discussed. The quality of the obtained structures is analyzed by means of 3D surface metrology microscope as well as SEM images.

  20. Numerical simulation of impurity desorption induced by nanosecond and femtosecond laser pulses

    SciTech Connect

    Chi Yinsheng; Lin Xiaohui; Chen Minhua; Chen Yunfei

    2006-08-01

    A model based on a stochastic process was developed to study the impurity molecule desorption from a substrate induced by nanosecond and femtosecond lasers. The dynamics of adsorbed molecules irradiated by the laser pulses can be considered to be a Brownian motion in the bath of excited energy carriers. A two-step model was used to describe the nonequilibrium heating process induced by the femtosecond laser pulses. The difference between the desorption processes induced by nanosecond and femtosecond lasers was discussed based on the numerical results for the desorption of CO molecules from a Ru surface. Results indicate that the femtosecond laser is a much better tool for desorption than the nanosecond laser.

  1. Evaluation of femtosecond laser-induced breakdown spectroscopy for explosive residue detection.

    PubMed

    De Lucia, Frank C; Gottfried, Jennifer L; Miziolek, Andrzej W

    2009-01-19

    Recently laser-induced breakdown spectroscopy (LIBS) has been investigated as a potential technique for trace explosive detection. Typically LIBS is performed using nanosecond laser pulses. For this work, we have investigated the use of femtosecond laser pulses for explosive residue detection at two different fluences. Femtosecond laser pulses have previously been shown to provide several advantages for laser ablation and other LIBS applications. We have collected LIBS spectra of several bulk explosives and explosive residues at different pulse durations and energies. In contrast to previous femtosecond LIBS spectra of explosives, we have observed atomic emission peaks for the constituent elements of explosives - carbon, hydrogen, nitrogen, and oxygen. Preliminary results indicate that several advantages attributed to femtosecond pulses are not realized at higher laser fluences. PMID:19158854

  2. Femtosecond laser-induced surface structures on carbon fibers.

    PubMed

    Sajzew, Roman; Schröder, Jan; Kunz, Clemens; Engel, Sebastian; Müller, Frank A; Gräf, Stephan

    2015-12-15

    The influence of different polarization states during the generation of periodic nanostructures on the surface of carbon fibers was investigated using a femtosecond laser with a pulse duration τ=300  fs, a wavelength λ=1025  nm, and a peak fluence F=4  J/cm². It was shown that linear polarization results in a well-aligned periodic pattern with different orders of magnitude concerning their period and an alignment parallel and perpendicular to fiber direction, respectively. For circular polarization, both types of uniform laser-induced periodic surface structures (LIPSS) patterns appear simultaneously with different dominance in dependence on the position at the fiber surface. Their orientation was explained by the polarization-dependent absorptivity and the geometrical anisotropy of the carbon fibers. PMID:26670499

  3. Dynamics of femtosecond laser produced tungsten nanoparticle plumes

    SciTech Connect

    Harilal, S. S.; Hassanein, A.; Farid, N.; Kozhevin, V. M.

    2013-11-28

    We investigated the expansion features of femtosecond laser generated tungsten nanoparticle plumes in vacuum. Fast gated images showed distinct two components expansion features, viz., plasma and nanoparticle plumes, separated by time of appearance. The persistence of plasma and nanoparticle plumes are ∼500 ns and ∼100 μs, respectively, and propagating with velocities differed by 25 times. The estimated temperature of the nanoparticles showed a decreasing trend with increasing time and space. Compared to low-Z materials (e.g., Si), ultrafast laser ablation of high-Z materials like W provides significantly higher nanoparticle yield. A comparison between the nanoparticle plumes generated by W and Si is also discussed along with other metals.

  4. Ablation and nanostructuring of metals by femtosecond laser pulses

    SciTech Connect

    Ashitkov, S I; Komarov, P S; Ovchinnikov, A V; Struleva, E V; Agranat, M B; Zhakhovskii, V V; Inogamov, N A

    2014-06-30

    Using an interferometric continuous monitoring technique, we have investigated the motion of the surface of an aluminium target in the case of femtosecond laser ablation at picosecond time delays relative to the instant of laser exposure. Measurements of the temporal target dispersion dynamics, molecular dynamics simulation results and the morphology of the ablation crater have demonstrated a thermomechanical (spall) nature of the disruption of the condensed phase due to the cavitation-driven formation and growth of vapour phase nuclei upon melt expansion, followed by the formation of surface nanostructures upon melt solidification. The tensile strength of heated aluminium in a condensed state has been determined experimentally at an expansion rate of ∼10{sup 9} s{sup -1}. (extreme light fields and their applications)

  5. Micro-structured femtosecond laser assisted FBG hydrogen sensor.

    PubMed

    Karanja, Joseph Muna; Dai, Yutang; Zhou, Xian; Liu, Bin; Yang, Minghong

    2015-11-30

    We discuss hydrogen sensors based on fiber Bragg gratings (FBGs) micro-machined by femtosecond laser to form microgrooves and sputtered with Pd/Ag composite film. The atomic ratio of the two metals is controlled at Pd:Ag = 3:1. At room temperature, the hydrogen sensitivity of the sensor probe micro-machined by 75 mW laser power and sputtered with 520 nm of Pd/Ag film is 16.5 pm/%H. Comparably, the standard FBG hydrogen sensitivity becomes 2.5 pm/%H towards the same 4% hydrogen concentration. At an ambient temperature of 35°C, the processed sensor head has a dramatic rise in hydrogen sensitivity. Besides, the sensor shows good response and repeatability during hydrogen concentration test. PMID:26698733

  6. Laser optoacoustic tomography for the study of femtosecond laser filaments in air

    NASA Astrophysics Data System (ADS)

    Bychkov, A. S.; Cherepetskaya, E. B.; Karabutov, A. A.; Makarov, V. A.

    2016-08-01

    We propose to use optoacoustic tomography to study the characteristics of femtosecond laser filamentation in air and condensed matter. The high spatial resolution of the proposed system, which consists of an array of broadband megahertz piezoelectric elements, ensures its effectiveness, despite the attenuation of ultrasonic waves in air.

  7. Fabrication of 3D microfluidic structures inside glass by femtosecond laser micromachining

    NASA Astrophysics Data System (ADS)

    Sugioka, Koji; Cheng, Ya

    2014-01-01

    Femtosecond lasers have opened up new avenues in materials processing due to their unique characteristics of ultrashort pulse widths and extremely high peak intensities. One of the most important features of femtosecond laser processing is that a femtosecond laser beam can induce strong absorption in even transparent materials due to nonlinear multiphoton absorption. This makes it possible to directly create three-dimensional (3D) microfluidic structures in glass that are of great use for fabrication of biochips. For fabrication of the 3D microfluidic structures, two technical approaches are being attempted. One of them employs femtosecond laser-induced internal modification of glass followed by wet chemical etching using an acid solution (Femtosecond laser-assisted wet chemical etching), while the other one performs femtosecond laser 3D ablation of the glass in distilled water (liquid-assisted femtosecond laser drilling). This paper provides a review on these two techniques for fabrication of 3D micro and nanofluidic structures in glass based on our development and experimental results.

  8. Possible evidence of Coulomb explosion in the femtosecond laser ablation of metal at low laser fluence

    NASA Astrophysics Data System (ADS)

    Li, Shuchang; Li, Suyu; Zhang, Fangjian; Tian, Dan; Li, He; Liu, Dunli; Jiang, Yuanfei; Chen, Anmin; Jin, Mingxing

    2015-11-01

    We use a computational model to study the ablation mechanism of metal target irradiated by femtosecond pulse laser. It is confirmed that the Coulomb explosion can occur during femtosecond laser ablation of metal. The influence of thermal ablation and Coulomb explosion on the ablation depth is respectively investigated. Comparing the calculated results with the experimental ones, we find that the theoretical results which consider the thermal ablation only agree well with the experimental ones at high laser fluence, and those which take the Coulomb explosion into account fit well with the experimental ones at lower laser fluence, which exactly explains the ablation mechanism. In contrast with the previous theoretical results which only consider the thermal ablation, our theoretical simulation describes the ablation mechanism straightforward by making comparison of ablation depth, and provides a more reasonable explanation that fits with the actual ablation process.

  9. A Fokker-Planck code for laser plasma interaction in femtosecond-laser shock peening

    NASA Astrophysics Data System (ADS)

    Ren, Zhencheng; Wang, Guo-Xiang; Ye, Chang; Dong, Yalin

    2016-03-01

    A Fokker-Planck code is developed to simulate the laser-plasma interaction in the femtosecond-laser shock peening and forming processes. A numerical scheme dealing with high-energy concentration and its resulting steep gradient are presented, and the source code is provided as supplementary material for further usage. The breakdown of the classical heat transport theory is observed when the laser intensity increases. The difference in heat flow between the classical theory and simulation is presented. It is found that the classical heat transport theory overestimates heat flow by orders of magnitude during femtosecond-laser shock peening or forming. As a result, the electron pressure can be underestimated using the classical hydrodynamic code.

  10. Active compensation of large dispersion of femtosecond pulses for precision laser ranging.

    PubMed

    Lee, Sang-Hyun; Lee, Joohyung; Kim, Young-Jin; Lee, Keunwoo; Kim, Seung-Woo

    2011-02-28

    We describe an active way of compensation for large dispersion induced in the femtosecond light pulses travelling in air for laser ranging. The pulse duration is consistently regulated at 250 fs by dispersion control, allowing sub-micrometer resolution in measuring long distances by means of time-of-flight measurement. This method could facilitate more reliable applications of femtosecond pulses for satellite laser ranging, laser altimetry and active LIDAR applications. PMID:21369227

  11. Sub-diffraction limited structuring of solid targets with femtosecond laser pulses.

    PubMed

    Korte, F; Adams, S; Egbert, A; Fallnich, C; Ostendorf, A; Nolte, S; Will, M; Ruske, J P; Chichkov, B; Tuennermann, A

    2000-07-17

    Possibilities to produce sub-diffraction limited structures in thin metal films and bulk dielectric materials using femtosecond laser pulses are investigated. The physics of ultrashort pulse laser ablation of solids is outlined. Results on the fabrication of sub-micrometer structures in 100-200 nm chrome-coated surfaces by direct ablative writing are reported. Polarization maintaining optical waveguides produced by femtosecond laser pulses inside crystalline quartz are demonstrated. PMID:19404368

  12. Fabrication of surface nanoscale axial photonics structures with a femtosecond laser.

    PubMed

    Shen, Fangcheng; Shu, Xuewen; Zhang, Lin; Sumetsky, M

    2016-06-15

    Surface nanoscale axial photonics (SNAP) structures are fabricated with a femtosecond laser for the first time, to the best of our knowledge. The inscriptions introduced by the laser pressurize the fiber and cause its nanoscale effective radius variation. We demonstrate the subangstrom precise fabrication of individual and coupled SNAP microresonators having the effective radius variation of several nanometers. Our results pave the way to a novel ultraprecise SNAP fabrication technology based on the femtosecond laser inscription. PMID:27304291

  13. Mechanism study of femtosecond laser induced selective metallization (FLISM) on glass surfaces

    NASA Astrophysics Data System (ADS)

    Xu, Jian; Liao, Yang; Zeng, Huidan; Cheng, Ya; Xu, Zhizhan; Sugioka, Koji; Midorikawa, Katsumi

    2008-07-01

    We investigate the mechanism of selective metallization on glass surfaces with the assistance of femtosecond laser irradiation followed by electroless plating. Irradiation of femtosecond laser makes it possible to selectively deposit copper microstructures in the irradiated area on glass surfaces coated with silver nitrate films. The energy-dispersive X-ray (EDX) analyses reveal that silver atoms are produced on the surface of grooves formed by laser ablation, which serve as catalysis seeds for subsequent electroless copper plating.

  14. Femtosecond Laser Synthesis of Multi-Element Nanocrystals

    SciTech Connect

    Dinh, L N; Trelenberg, T; Torralva, B; Stuart, B C; Balooch, M

    2003-01-08

    We studied the conditions under which short-pulsed laser deposited (PLD) stoichiometric multi-element nanocrystals of GaAs,InP,CoPt and Inconel (an alloy of Cr, Fe and Ni) are formed. The properties of the PLD nanoclusters and the irradiated targets were investigated as a function of the laser pulse-length (150 fs-500 ps) and the inert background gas pressure in the synthesis chamber (microTorr to hundreds of Torr). Our results reveal that the formation of stoichiometric GaAs nanocrystals required ablating a GaAs target with a shorter than 25 ps laser in a {ge} 50 miliTorr of inert background pressure. For InP, a mixture of stoichiometric InP and In nanocrystals with an InP/In ratio of {approx} 1 resulted upon ablating an InP target in Ar at 1 Torr. This InP/In ratio increased to {approx} 5 when ablating the InP target in an Ar pressure of 750 Torr. In case of CoPt alloy, the stoichiometry in the target was not reflected in the collected nanocluster films, independent of the background gas pressure. Interestingly, the stoichiometry of the target was found in the collected nanocluster films when an Inconel target was ablated by a femtosecond laser even in vacuum. It is noted that the constituents of Inconel (Cr, Fe and Ni) have similar vapor pressures while Co and Pt do not. Our experimental results suggest that the stoichiometries of the PLD multi-element nanoclusters are closer with those of the targets when shorter than 25 ps lasers are used. However, this does not imply that simply irradiating a multi-element target in vacuum with a shorter than 25 ps pulse-length laser would automatically result in the formation of stoichiometric nanocrystals. The preservation of the stoichiometry of the irradiated target and the formation of stoichiometric semiconductor nanocrystals require ablating the targets with a shorter than 25 ps laser in a background gas. The minimum background gas pressure is materials dependent. And for metal alloys, the stoichiometry of the ablated

  15. Femtosecond laser fabrication of gold nanorod/polymer composite microstructures

    NASA Astrophysics Data System (ADS)

    Masui, Kyoko; Shoji, Satoru; Ushiba, Shota; Duan, Xuan-Ming; Kawata, Satoshi

    2012-10-01

    We present a fabrication method of gold nanorod/ polymer composite microstructures by means of a femtosecond near-infrared laser light. The mechanism of this method is based on a cooperation of two optical reactions; two-photon polymerization (TPP) reaction only at the surface of gold nanorods, and optical accumulation of gold nanorods in photo-polymerizable resin. Gold nanorods were mass-produced by seed mediated growth method, and were mono-dispersed in photo-resin. The wavelength of the laser light was tuned resonant to two-photon absorption of the photo-resin, and also close to a longitudinal local surface plasmon resonance (LSPR) mode of the gold nanorods. The laser light excited LSPR onto gold nanorods, resulting in the formation of thin polymer layer only at their surface through TPP. Concurrently occurring optical accumulation of gold nanorods by continuous irradiation of laser light, gold nanorods got together into focus spot. The TPP layer at the surface of gold nanorods worked as a glue to stick one another for forming their aggregated structure in micro/nano scale. By controlling the intensity and the exposure time of laser light, an optimal condition was found to induce dominant polymerization without any thermal damages. The scanning of the focus spot makes it possible to create arbitrary micro/nano structures. This method has a potential to create plasmonic optical materials by controlling the alignment of gold nanorods.

  16. Space-selective laser joining of dissimilar transparent materials using femtosecond laser pulses

    SciTech Connect

    Watanabe, Wataru; Onda, Satoshi; Tamaki, Takayuki; Itoh, Kazuyoshi; Nishii, Junji

    2006-07-10

    We report on the joining of dissimilar transparent materials based on localized melting and resolidification of the materials only around the focal volume due to nonlinear absorption of focused femtosecond laser pulses. We demonstrate the joining of borosilicate glass and fused silica, whose coefficients of thermal expansion are different. The joint strength and the transmittance through joint volume were investigated by varying the translation velocity of the sample and the pulse energy of the irradiated laser pulses.

  17. Self-organized Propagation of Femtosecond Laser Filamentation in Air

    NASA Astrophysics Data System (ADS)

    Zhang, Jie; Hao, Zuoqiang; Xi, Tingting; Lu, Xin; Zhang, Zhe; Yang, Hui; Jin, Zhan; Wang, Zhaohua; Wei, Zhiyi

    A long plasma channel is formed with a length up to a few hundred meters when intense femtosecond laser pulses propagate in air. We find that the propagation of the filaments in the channel shows a very complicated process including the evolution from a single filament into two and three and even more distinct filaments periodically, and the merging of multiple filaments into two filaments that propagate stably and fade away eventually. From the point of view of applications, the lifetime of the plasma channel can be prolonged to the order of microseconds when another sub-ns laser pulse is introduced. The filaments' distribution is optimized using a pinhole with different diameters. Our experiments also demonstrate simultaneous triggering and guiding of large gap discharges in air by laser filaments. A new concept of "laser plasma channel propulsion" is proposed. It is demonstrated that the plasma channel can continuously propel a light paper airplane without complicated focusing optics. As for the long distance propagation of the laser pulses, the filamentation process and the surpercontinuum (SC) emission are closely dependent on the initial negative chirp and the divergence angle of the laser beam. Most of laser energy deposited in the background serves as an energy reservoir for further propagation of the filamentation. We have shown that an energy reservoir over ten times the size of the filament core (mm size) is necessary to feed a single filament undisturbed propagation. At last, the characteristics of the multiple filaments formed by pre-focused and freely propagating fs laser pulses are investigated and compared.

  18. Synthesis of submicron metastable phase of silicon using femtosecond laser-driven shock wave

    SciTech Connect

    Tsujino, Masashi; Sano, Tomokazu; Sakata, Osami; Ozaki, Norimasa; Kodama, Ryosuke; Kimura, Shigeru; Takeda, Shingo; Kobayashi, Kojiro F.; Hirose, Akio

    2011-12-15

    We measured the grain size of metastable phase of Si synthesized by shock compression. We analyzed the crystalline structures of the femtosecond laser-driven shock compressed silicon with x-ray diffraction measurements. We found that submicron grains of metastable Si-VIII exist in the silicon. We suggest that the pressure loading time is too short for the nucleated high-pressure phases to grow in case of the femtosecond laser-driven shock compression, therefore Si-VIII grains of submicron size are obtained. We are expecting to discover other unique crystalline structures induced by the femtosecond laser-driven shock wave.

  19. Formation of periodic nanostructures using a femtosecond laser to control cell spreading on titanium

    NASA Astrophysics Data System (ADS)

    Shinonaga, T.; Tsukamoto, M.; Kawa, T.; Chen, P.; Nagai, A.; Hanawa, T.

    2015-06-01

    Although titanium (Ti) is a common biomaterial, controlling cell spreading by forming periodic structures using a femtosecond laser should improve its biocompatibility. Herein we investigate the influence of periodic nanostructures formed on the surface of a Ti plate on cell spreading. Nanostructures with a periodicity of 590 nm are formed using a femtosecond laser with a wavelength of 775 nm. Cell spreading on the plate without period structures lacks a definite direction, whereas cell spreading on the Ti plate with periodic structures occurs along the grooves, suggesting that forming periodic structures via a femtosecond laser can control cell spreading.

  20. Measurement of ablation threshold of oxide-film-coated aluminium nanoparticles irradiated by femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Chefonov, O. V.; Ovchinnikov, A. V.; Il'ina, I. V.; Agranat, M. B.

    2016-03-01

    We report the results of experiments on estimation of femtosecond laser threshold intensity at which nanoparticles are removed from the substrate surface. The studies are performed with nanoparticles obtained by femtosecond laser ablation of pure aluminium in distilled water. The attenuation (or extinction, i.e. absorption and scattering) spectra of nanoparticles are measured at room temperature in the UV and optical wavelength ranges. The size of nanoparticles is determined using atomic force microscopy. A new method of scanning photoluminescence is proposed to evaluate the threshold of nanoparticle removal from the surface of a glass substrate exposed to IR femtosecond laser pulses with intensities 1011 – 1013 W cm-2.

  1. The fluence threshold of femtosecond laser blackening of metals: The effect of laser-induced ripples

    NASA Astrophysics Data System (ADS)

    Ou, Zhigui; Huang, Min; Zhao, Fuli

    2016-05-01

    With the primary controlling factor of the laser fluence, we have investigated femtosecond laser blackening of stainless steel, brass, and aluminum in visible light range. In general, low reflectance about 5% can be achieved in appropriate ranges of laser fluences for all the treated metal surfaces. Significantly, towards stainless steel and brass a fluence threshold of blackening emerges unusually: a dramatic reflectance decline occurs in a specific, narrow fluence range. In contrast, towards aluminum the reflectance declines steadily over a wide fluence range instead of the threshold-like behavior from steel and brass. The morphological characteristics and corresponding reflectance spectra of the treated surfaces indicates that the blackening threshold of stainless steel and brass corresponds to the fluence threshold of laser-induced subwavelength ripples. Such periodic ripples growing rapidly near ablation threshold absorb visible light efficiently through grating coupling and cavity trapping promoted by surface plasmon polaritons. Whereas, for aluminum, with fluence increasing the looming ripples are greatly suppressed by re-deposited nanoparticle aggregates that present intrinsic colors other than black, and until the formation of large scale "ravines" provided with strong light-trapping, sufficient blackening is achieved. In short, there are different fluence dependencies for femtosecond laser blackening of metals, and the specific blackening fluence threshold for certain metals in the visible range originates in the definite fluence threshold of femtosecond laser-induced ripples.

  2. Laser damage resistant pits in dielectric coatings created by femtosecond laser machining

    SciTech Connect

    Wolfe, J; Roger Qiu, ,; Stolz, C; Thomas, M; Martinez, C; Ozkan, A

    2009-11-03

    Replacing growing damage sites with benign, laser damage resistant features in multilayer dielectric films may enable large mirrors to be operated at significantly higher fluences. Laser damage resistant features have been created in high reflecting coatings on glass substrates using femtosecond laser machining. These prototype features have been damage tested to over 40 J/cm{sup 2} (1064nm, 3ns pulselength) and have been shown not to damage upon repeated irradiation at 40J/cm{sup 2}. Further work to optimize feature shape and laser machining parameters is ongoing.

  3. Generation of elliptically polarized nitrogen ion laser fields using two-color femtosecond laser pulses

    PubMed Central

    Li, Ziting; Zeng, Bin; Chu, Wei; Xie, Hongqiang; Yao, Jinping; Li, Guihua; Qiao, Lingling; Wang, Zhanshan; Cheng, Ya

    2016-01-01

    We experimentally investigate generation of nitrogen molecular ion () lasers with two femtosecond laser pulses at different wavelengths. The first pulse serves as the pump which ionizes the nitrogen molecules and excites the molecular ions to excited electronic states. The second pulse serves as the probe which leads to stimulated emission from the excited molecular ions. We observe that changing the angle between the polarization directions of the two pulses gives rise to elliptically polarized laser fields, which is interpreted as a result of strong birefringence of the gain medium near the wavelengths of the laser. PMID:26888182

  4. Combining femtosecond laser ablation and diode laser welding in lamellar and endothelial corneal transplants

    NASA Astrophysics Data System (ADS)

    Pini, Roberto; Rossi, Francesca; Matteini, Paolo; Ratto, Fulvio; Menabuoni, Luca; Lenzetti, Ivo; Yoo, Sonia H.; Parel, Jean-Marie

    2008-02-01

    Based on our previous clinical experiences in minimally invasive diode laser-induced welding of corneal tissue in penetrating keratoplasty (PK), i.e. full-thickness transplant of the cornea, we combined this technique with the use of a femtosecond laser for applications in lamellar (LK) and endothelial (EK) keratoplasty. In LK, the femtosecond laser was used to prepare donor button and recipient corneal bed; the wound edges were stained with a water solution of Indocyanine Green (ICG) and then irradiated with a diode laser emitting in CW mode to induce stromal welding. Intraoperatory observations and follow-up results up to 6 months indicated the formation of a smooth stromal interface, total absence of edema as well as inflammation, and reduction of post-operative astigmatism, as compared with conventional suturing procedures. In EK the femtosecond laser was used for the preparation of a 100 μm thick, 8.5mm diameter donor corneal endothelium flap. The flap stromal side was stained with ICG. After stripping the recipient Descemet's membrane and endothelium, the donor flap was positioned in the anterior chamber on the inner face of the cornea by an air bubble and secured to the recipient cornea by diode laser pulses delivered by means of a fiberoptic contact probe introduced in the anterior chamber, which produced welding spots of 200 μm diameter. Femtosecond laser sculpturing of the donor cornea provided lamellar and endothelial flaps of preset and constant thickness. Diode laserinduced welding showed a unique potential to permanently secure the donor flap in place, avoiding postoperative displacement and inflammation reaction.

  5. Femtosecond laser-induced microstructures in glasses and applications in micro-optics.

    PubMed

    Qiu, Jianrong

    2004-01-01

    Femtosecond laser has been widely used in microscopic modifications to materials due to its ultra-short laser pulse and ultrahigh light intensity. When a transparent material e.g. glass is irradiated by a tightly focused femtosecond laser, the photo-induced reaction is expected to occur only near the focused part of the laser beam inside the glass due to the multiphoton processes. We observed various induced structures e.g. color center defects, refractive index change, micro-void and micro-crack, in glasses after the femtosecond laser irradiation. In this paper, we review the femtosecond laser induced phenomena and discuss the mechanisms of the observed phenomena. We also introduce the fabrication of various micro-optical components, e.g. optical waveguide, micro-grating, micro-lens, fiber attenuator, 3-dimensional optical memory by using the femtosecond laser-induced structures. The femtosecond laser will open new possibilities in the fabrication of micro-optical components with various optical functions. PMID:15057868

  6. Using femtosecond lasers to modify sizes of gold nanoparticles

    NASA Astrophysics Data System (ADS)

    da Silva Cordeiro, Thiago; Almeida de Matos, Ricardo; Silva, Flávia Rodrigues de Oliveira; Vieira, Nilson D.; Courrol, Lilia C.; Samad, Ricardo E.

    2016-04-01

    Metallic nanoparticles are important on several scientific, medical and industrial areas. The control of nanoparticles characteristics has fundamental importance to increase the efficiency on the processes and applications in which they are employed. The metallic nanoparticles present specific surface plasmon resonances (SPR). These resonances are related with the collective oscillations of the electrons presents on the metallic nanoparticle. The SPR is determined by the potential defined by the nanoparticle size and geometry. There are several methods of producing gold nanoparticles, including the use of toxic chemical polymers. We already reported the use of natural polymers, as for example, the agar-agar, to produce metallic nanoparticles under xenon lamp irradiation. This technique is characterized as a "green" synthesis because the natural polymers are inoffensive to the environment. We report a technique to produce metallic nanoparticles and change its geometrical and dimensional characteristics using a femtosecond laser. The 1 ml initial solution was irradiate using a laser beam with 380 mW, 1 kHz and 40 nm of bandwidth centered at 800 nm. The setup uses an Acousto-optic modulator, Dazzler, to change the pulses spectral profiles by introduction of several orders of phase, resulting in different temporal energy distributions. The use of Dazzler has the objective of change the gold nanoparticles average size by the changing of temporal energy distributions of the laser pulses incident in the sample. After the laser irradiation, the gold nanoparticles average diameter were less than 15 nm.

  7. Optical Spectroscopy Using Gas-Phase Femtosecond Laser Filamentation

    NASA Astrophysics Data System (ADS)

    Odhner, Johanan; Levis, Robert

    2014-04-01

    Femtosecond laser filamentation occurs as a dynamic balance between the self-focusing and plasma defocusing of a laser pulse to produce ultrashort radiation as brief as a few optical cycles. This unique source has many properties that make it attractive as a nonlinear optical tool for spectroscopy, such as propagation at high intensities over extended distances, self-shortening, white-light generation, and the formation of an underdense plasma. The plasma channel that constitutes a single filament and whose position in space can be controlled by its input parameters can span meters-long distances, whereas multifilamentation of a laser beam can be sustained up to hundreds of meters in the atmosphere. In this review, we briefly summarize the current understanding and use of laser filaments for spectroscopic investigations of molecules. A theoretical framework of filamentation is presented, along with recent experimental evidence supporting the established understanding of filamentation. Investigations carried out on vibrational and rotational spectroscopy, filament-induced breakdown, fluorescence spectroscopy, and backward lasing are discussed.

  8. Optical spectroscopy using gas-phase femtosecond laser filamentation.

    PubMed

    Odhner, Johanan; Levis, Robert

    2014-01-01

    Femtosecond laser filamentation occurs as a dynamic balance between the self-focusing and plasma defocusing of a laser pulse to produce ultrashort radiation as brief as a few optical cycles. This unique source has many properties that make it attractive as a nonlinear optical tool for spectroscopy, such as propagation at high intensities over extended distances, self-shortening, white-light generation, and the formation of an underdense plasma. The plasma channel that constitutes a single filament and whose position in space can be controlled by its input parameters can span meters-long distances, whereas multifilamentation of a laser beam can be sustained up to hundreds of meters in the atmosphere. In this review, we briefly summarize the current understanding and use of laser filaments for spectroscopic investigations of molecules. A theoretical framework of filamentation is presented, along with recent experimental evidence supporting the established understanding of filamentation. Investigations carried out on vibrational and rotational spectroscopy, filament-induced breakdown, fluorescence spectroscopy, and backward lasing are discussed. PMID:24423375

  9. Robust Non-Wetting PTFE Surfaces by Femtosecond Laser Machining

    PubMed Central

    Liang, Fang; Lehr, Jorge; Danielczak, Lisa; Leask, Richard; Kietzig, Anne-Marie

    2014-01-01

    Nature shows many examples of surfaces with extraordinary wettability, which can often be associated with particular air-trapping surface patterns. Here, robust non-wetting surfaces have been created by femtosecond laser ablation of polytetrafluoroethylene (PTFE). The laser-created surface structure resembles a forest of entangled fibers, which support structural superhydrophobicity even when the surface chemistry is changed by gold coating. SEM analysis showed that the degree of entanglement of hairs and the depth of the forest pattern correlates positively with accumulated laser fluence and can thus be influenced by altering various laser process parameters. The resulting fibrous surfaces exhibit a tremendous decrease in wettability compared to smooth PTFE surfaces; droplets impacting the virgin or gold coated PTFE forest do not wet the surface but bounce off. Exploratory bioadhesion experiments showed that the surfaces are truly air-trapping and do not support cell adhesion. Therewith, the created surfaces successfully mimic biological surfaces such as insect wings with robust anti-wetting behavior and potential for antiadhesive applications. In addition, the fabrication can be carried out in one process step, and our results clearly show the insensitivity of the resulting non-wetting behavior to variations in the process parameters, both of which make it a strong candidate for industrial applications. PMID:25110862

  10. Robust non-wetting PTFE surfaces by femtosecond laser machining.

    PubMed

    Liang, Fang; Lehr, Jorge; Danielczak, Lisa; Leask, Richard; Kietzig, Anne-Marie

    2014-01-01

    Nature shows many examples of surfaces with extraordinary wettability,which can often be associated with particular air-trapping surface patterns. Here,robust non-wetting surfaces have been created by femtosecond laser ablation of polytetrafluoroethylene (PTFE). The laser-created surface structure resembles a forest of entangled fibers, which support structural superhydrophobicity even when the surface chemistry is changed by gold coating. SEM analysis showed that the degree of entanglement of hairs and the depth of the forest pattern correlates positively with accumulated laser fluence and can thus be influenced by altering various laser process parameters. The resulting fibrous surfaces exhibit a tremendous decrease in wettability compared to smooth PTFE surfaces; droplets impacting the virgin or gold coated PTFE forest do not wet the surface but bounce off. Exploratory bioadhesion experiments showed that the surfaces are truly air-trapping and do not support cell adhesion. Therewith, the created surfaces successfully mimic biological surfaces such as insect wings with robust anti-wetting behavior and potential for antiadhesive applications. In addition, the fabrication can be carried out in one process step, and our results clearly show the insensitivity of the resulting non-wetting behavior to variations in the process parameters,both of which make it a strong candidate for industrial applications. PMID:25110862

  11. Formation of Si structure in glass with a femtosecond laser

    NASA Astrophysics Data System (ADS)

    Miura, Kiyotaka; Hirao, Kazuyuki; Shimotsuma, Yasuhiko; Sakakura, Masaaki; Kanehira, Shingo

    2008-10-01

    Mixing metallic Al into the starting material for silicate glass is proposed as a means of forming Si structures in glass. We confirmed that Si nanocrystals are space-selectively deposited in silicate glass via a thermite reaction triggered by femtosecond laser pulses. Small Si particles were transformed into larger, but still micrometer sized, Si particles by laser irradiation. These structures grew to micro-size particles due to the thermite reaction promoted by heat treatment. We discuss what effect the irradiation of the focused laser pulse had on the Si deposition process in the laser-irradiated region. Localized high temperatures and pressures and generation of shock waves appear to be very important in forming Si-rich structures that contribute to the growth of Si particles. The diffusion of calcium ions by the generation of shock waves and the presence of Al-rich structures is important for forming Si-rich structures such as Si clusters, which is achieved by continuously breaking Si-O bonds using localized high temperatures.

  12. Transient light absorption induced in glassby femtosecond laser pulses

    SciTech Connect

    Blonskii, I V; Kadan, V N; Pavlov, I A; Kryuchkov, N N; Shpotyuk, O I

    2009-10-31

    The dynamics of the transient light absorption induced in K8 optical glass by filamented femtosecond laser pulses have been studied using time-resolved transmitted-light microscopy at wavelengths from 450 to 700 nm. The transient absorption measured as a function of probe beam wavelength is compared to that predicted by the Drude plasma model. We conclude that, just 450 fs after a pump pulse, the transient absorption is dominated by transient electronic states, presumably, self-trapped excitons, with an excitation energy of 2.6 - 2.7 eV. These states are filled with free-carriers from a long-lived plasma, which acts as a 'carrier reservoir'. The relaxation of transient absorption has two components. The slow component, with {tau}{sub 1} {approx} 17-17.5 ps, is governed by the plasma thermalisation time, whereas the second, with {tau}{sub 1} >> 300 ps, is determined by the plasma lifetime. (nonlinear optical phenomena)

  13. Nonlinear Raman-Nath diffraction of femtosecond laser pulses.

    PubMed

    Vyunishev, A M; Slabko, V V; Baturin, I S; Akhmatkhanov, A R; Shur, V Ya

    2014-07-15

    We study the nonlinear Raman-Nath diffraction (NRND) of femtosecond laser pulses in a 1D periodic nonlinear photonic structure. The calculated second-harmonic spectra represent frequency combs for different orders of transverse phase matching. These frequency combs are in close analogy with the well-known spectral Maker fringes observed in single crystals. The spectral intensity of the second harmonic experiences a redshift with a propagation angle, which is opposite the case of Čerenkov nonlinear diffraction. We analyze how NRND is affected by the group-velocity mismatch between fundamental and second-harmonic pulses and by the parameters of the structure. Our experimental results prove the theoretical predictions. PMID:25121694

  14. Removal of Retained Descemets Membrane Using Femtosecond Laser

    PubMed Central

    May, William; Alrashidi, Sultan; Daoud, Yassine J.

    2016-01-01

    We present a unique method of retrocorneal membrane removal with a femtosecond laser (FSL). A 22-year-old male who had undergone penetrating keratoplasty had a retained retrocorneal membrane and a double anterior chamber postoperatively. The membrane was dissected completely with the FSL and the free-floating membrane was removed. Histopathological evaluation confirmed the diagnosis of retained Descemets membrane (DM). There was improvement in uncorrected visual acuity from 20/300 to 20/50. Central corneal endothelial cell count was 810 cells/mm2 preoperatively and 778 cells/mm2 postoperatively. Inadvertent retention of DM may be safely treated with the FSL. Clarity and viability of the existing graft can be maintained. PMID:27555712

  15. Spectroscopic analysis of femtosecond laser plasma filament in air

    NASA Astrophysics Data System (ADS)

    Bernhardt, J.; Liu, W.; Théberge, F.; Xu, H. L.; Daigle, J. F.; Châteauneuf, M.; Dubois, J.; Chin, S. L.

    2008-03-01

    We report a spectroscopic analysis of a filament generated by a femtosecond laser pulse in air. In the filament spectra, the characteristic Stark broadened atomic oxygen triplet centered at 777.4 nm has been observed. The measured electron impact Stark broadening parameter of the triplet is larger than the theoretical value by Griem [H.R. Griem, Plasma Spectroscopy, McGraw Hill, New York, 1964] by a factor 6.7 . Using the experimental value 0.0166nm , the plasma densities derived from Stark broadening agree well with those most recently obtained from Théberge et al.'s measurement of the nitrogen fluorescence calibrated by longitudinal diffraction [F. Théberge, W. Liu, P.T. Simard, A. Becker, S. L. Chin, Phys. Rev. E 74 (2006) 036406]. However, the Stark broadening approach is much simpler and can be used to non-invasively measure the filament plasma density distribution in air under different propagation conditions.

  16. Hole drilling on glass optical fibers by a femtosecond laser

    NASA Astrophysics Data System (ADS)

    Hamasaki, Masayuki; Gouya, Kenji; Watanabe, Kazuhiro

    2012-01-01

    A novel optical fiber sensor has been developed for gaseous material detection by means of a femto-second laser which has ultrashort pulse and ultrahigh peak power. This sensor has attractive sensor potion consisted of drilling holes array which is machined on the glass optical fiber. Additionally, the sensor potion is coated with thin gold film. This work expects that an interaction could be induced between transmitted light through fiber core and a bottom of the drilled holes which reaches the fiber core. The interaction could induce near-field optical phenomenon excited by transmitted light through the fiber core. This scheme could make it possible to detect gaseous-material phase substances around the optical fiber. In this study, we found that localized surface plasmon (LSP) was excited by the transmitted light through the fiber core. This paper shows experiment to obtain optimum irradiation conditions and investigation for sensor principle for the development of a novel fiber sensor.

  17. [Recent advances in femtosecond laser-assisted cataract surgery].

    PubMed

    Yu, Yin-hui; Yao, Ke

    2013-05-01

    As the leading cause of blindness, the type of surgery performed to remove cataracts has evolved from Intracapsular to Extracapsular and to phacoemulsification. Advantages of femtosecond laser include high instantaneous power, strong penetration, short pulse-duration and micro-precision present superior accuracy, predictability and safety to cataract surgery, while also minimizing injury to surrounding ocular tissue. It mainly assists in the procedures of anterior capsulotomy, lens fragmentation, clear corneal incision and limbal relaxing incision creation. However, compared to conventional phacoemulsification, problems such as the minimization of complications and difficulties in conducting peer-reviewed studies with a longer follow-up period and large sample, as well as coverage of added costs remain untracked.The purpose of this review is to outline the advantages and disadvantages as well as clinical value of this evolving technology compared to conventional phacoemulsification. PMID:24021187

  18. Polarization maintaining linear cavity Er-doped fiber femtosecond laser

    NASA Astrophysics Data System (ADS)

    Jang, Heesuk; Jang, Yoon-Soo; Kim, Seungman; Lee, Keunwoo; Han, Seongheum; Kim, Young-Jin; Kim, Seung-Woo

    2015-10-01

    We present a polarization-maintaining (PM) type of Er-doped fiber linear oscillator designed to produce femtosecond laser pulses with high operational stability. Mode locking is activated using a semiconductor saturable absorber mirror (SESAM) attached to one end of the linear PM oscillator. To avoid heat damage, the SESAM is mounted on a copper-silicon-layered heat sink and connected to the linear oscillator through a fiber buffer dissipating the residual pump power. A long-term stability test is performed to prove that the proposed oscillator design maintains a soliton-mode single-pulse operation without breakdown of mode locking over a week period. With addition of an Er-doped fiber amplifier, the output power is raised to 180 mW with 60 fs pulse duration, from which an octave-spanning supercontinuum is produced.

  19. Noise properties of microwave signals synthesized with femtosecond lasers.

    PubMed

    Ivanov, Eugene N; McFerran, John J; Diddams, Scott A; Hollberg, Leo

    2007-04-01

    We discuss various aspects of high resolution measurements of phase fluctuations at microwave frequencies. This includes methods to achieve thermal noise limited sensitivity, along with the improved immunity to oscillator amplitude noise. A few prototype measurement systems were developed to measure phase fluctuations of microwave signals extracted from the optical pulse trains generated by femtosecond lasers. This enabled first reliable measurements of the excess phase noise associated with optical-to-microwave frequency division. The spectral density of the excess phase noise was found to be -140 dBc/Hz at 100 Hz offset from the 10 GHz carrier which was almost 40 dB better than that of a high quality microwave synthesizer. PMID:17441583

  20. Composition analysis by scanning femtosecond laser ultraprobing (CASFLU).

    DOEpatents

    Ishikawa, Muriel Y.; Wood, Lowell L.; Campbell, E. Michael; Stuart, Brent C.; Perry, Michael D.

    2002-01-01

    The composition analysis by scanning femtosecond ultraprobing (CASFLU) technology scans a focused train of extremely short-duration, very intense laser pulses across a sample. The partially-ionized plasma ablated by each pulse is spectrometrically analyzed in real time, determining the ablated material's composition. The steering of the scanned beam thus is computer directed to either continue ablative material-removal at the same site or to successively remove nearby material for the same type of composition analysis. This invention has utility in high-speed chemical-elemental, molecular-fragment and isotopic analyses of the microstructure composition of complex objects, e.g., the oxygen isotopic compositions of large populations of single osteons in bone.

  1. Carrier dynamics in femtosecond-laser-excited bismuth telluride

    NASA Astrophysics Data System (ADS)

    Wang, J. L.; Guo, L.; Ling, C.; Song, Y. M.; Xu, X. F.; Ni, Z. H.; Chen, Y. F.

    2016-04-01

    The carrier dynamics of B i2T e3 is studied using the femtosecond pump-probe technique. Three distinct processes, including free carrier absorption, band filling, and electron-hole recombination, are found to contribute to the reflectivity changes. The two-temperature model is used to describe the intraband energy relaxation process of carriers, and the Drude contribution well explains the intensity dependence of the peak values of the nonoscillatory component in the reflectivity signal. The combined effects of free carrier absorption and band filling result in a reflection minimum at about 2 ps after laser excitation. The nonzero background signal increases linearly with the pump fluence, which is attributed to the electron-hole recombination. Finally, our results provide an illustration of investigating the carrier dynamics in semiconductors from the ultrafast reflectivity spectra.

  2. Optical vibration sensor fabricated by femtosecond laser micromachining

    SciTech Connect

    Kamata, Masanao; Obara, Minoru; Gattass, Rafael R.; Cerami, Loren R.; Mazur, Eric

    2005-08-01

    We fabricated an optical vibration sensor using a high-repetition rate femtosecond laser oscillator. The sensor consists of a single straight waveguide written across a series of three pieces of glass. The central piece is mounted on a suspended beam to make it sensitive to mechanical vibration, acceleration, or external forces. Displacement of the central piece is detected by measuring the change in optical transmission through the waveguide. The resulting sensor is small, simple, and requires no alignment. The sensor has a linear response over the frequency range 20 Hz-2 kHz, can detect accelerations as small as 0.01 m/s{sup 2}, and is nearly temperature independent.

  3. Removal of Retained Descemets Membrane Using Femtosecond Laser.

    PubMed

    May, William; Alrashidi, Sultan; Daoud, Yassine J

    2016-01-01

    We present a unique method of retrocorneal membrane removal with a femtosecond laser (FSL). A 22-year-old male who had undergone penetrating keratoplasty had a retained retrocorneal membrane and a double anterior chamber postoperatively. The membrane was dissected completely with the FSL and the free-floating membrane was removed. Histopathological evaluation confirmed the diagnosis of retained Descemets membrane (DM). There was improvement in uncorrected visual acuity from 20/300 to 20/50. Central corneal endothelial cell count was 810 cells/mm(2) preoperatively and 778 cells/mm(2) postoperatively. Inadvertent retention of DM may be safely treated with the FSL. Clarity and viability of the existing graft can be maintained. PMID:27555712

  4. Mimicking subsecond neurotransmitter dynamics with femtosecond laser stimulated nanosystems

    NASA Astrophysics Data System (ADS)

    Nakano, Takashi; Chin, Catherine; Myint, David Mo Aung; Tan, Eng Wui; Hale, Peter John; Krishna M., Bala Murali; Reynolds, John N. J.; Wickens, Jeff; Dani, Keshav M.

    2014-06-01

    Existing nanoscale chemical delivery systems target diseased cells over long, sustained periods of time, typically through one-time, destructive triggering. Future directions lie in the development of fast and robust techniques capable of reproducing the pulsatile chemical activity of living organisms, thereby allowing us to mimic biofunctionality. Here, we demonstrate that by applying programmed femtosecond laser pulses to robust, nanoscale liposome structures containing dopamine, we achieve sub-second, controlled release of dopamine - a key neurotransmitter of the central nervous system - thereby replicating its release profile in the brain. The fast delivery system provides a powerful new interface with neural circuits, and to the larger range of biological functions that operate on this short timescale.

  5. Human cadaver retina model for retinal heating during corneal surgery with a femtosecond laser

    NASA Astrophysics Data System (ADS)

    Sun, Hui; Fan, Zhongwei; Yun, Jin; Zhao, Tianzhuo; Yan, Ying; Kurtz, Ron M.; Juhasz, Tibor

    2014-02-01

    Femtosecond lasers are widely used in everyday clinical procedures to perform minimally invasive corneal refractive surgery. The intralase femtosecond laser (AMO Corp. Santa Ana, CA) is a common example of such a laser. In the present study a numerical simulation was developed to quantify the temperature rise in the retina during femtosecond intracorneal surgery. Also, ex-vivo retinal heating due to laser irradiation was measured with an infrared thermal camera (Fluke Corp. Everett, WA) as a validation of the simulation. A computer simulation was developed using Comsol Multiphysics to calculate the temperature rise in the cadaver retina during femtosecond laser corneal surgery. The simulation showed a temperature rise of less than 0.3 degrees for realistic pulse energies for the various repetition rates. Human cadaver retinas were irradiated with a 150 kHz Intralase femtosecond laser and the temperature rise was measured withan infrared thermal camera. Thermal camera measurements are in agreement with the simulation. During routine femtosecond laser corneal surgery with normal clinical parameters, the temperature rise is well beneath the threshold for retina damage. The simulation predictions are in agreement with thermal measurements providing a level of experimental validation.

  6. Fast femtosecond laser ablation for efficient cutting of sintered alumina substrates

    NASA Astrophysics Data System (ADS)

    Oosterbeek, Reece N.; Ward, Thomas; Ashforth, Simon; Bodley, Owen; Rodda, Andrew E.; Simpson, M. Cather

    2016-09-01

    Fast, accurate cutting of technical ceramics is a significant technological challenge because of these materials' typical high mechanical strength and thermal resistance. Femtosecond pulsed lasers offer significant promise for meeting this challenge. Femtosecond pulses can machine nearly any material with small kerf and little to no collateral damage to the surrounding material. The main drawback to femtosecond laser machining of ceramics is slow processing speed. In this work we report on the improvement of femtosecond laser cutting of sintered alumina substrates through optimisation of laser processing parameters. The femtosecond laser ablation thresholds for sintered alumina were measured using the diagonal scan method. Incubation effects were found to fit a defect accumulation model, with Fth,1=6.0 J/cm2 (±0.3) and Fth,∞=2.5 J/cm2 (±0.2). The focal length and depth, laser power, number of passes, and material translation speed were optimised for ablation speed and high quality. Optimal conditions of 500 mW power, 100 mm focal length, 2000 μm/s material translation speed, with 14 passes, produced complete cutting of the alumina substrate at an overall processing speed of 143 μm/s - more than 4 times faster than the maximum reported overall processing speed previously achieved by Wang et al. [1]. This process significantly increases processing speeds of alumina substrates, thereby reducing costs, making femtosecond laser machining a more viable option for industrial users.

  7. Femtosecond laser waveguide writing in ternary zinc magnesium phosphate glasses

    NASA Astrophysics Data System (ADS)

    Skovorodnikov, Nikolay

    Femtosecond (fs) pulsed laser inscription was used to fabricate optical waveguides in ternary zinc magnesium phosphate glasses with different compositions. The main goal of this work was to find a reliable dielectric material for fs-laser waveguide writing, which has particular physical properties. The material is to be mechanically robust and chemically durable and is to exhibit positive refractive index change under fs-laser irradiation. Besides, such phosphate glass structures possess an advantageous high solubility of rare-earth ions, which can be potentially exploited for the fabrication of active photonic devices. In order to produce optical changes a fs-laser beam was focused inside the material so a sufficient intensity was reached and permanent structural modification could be induced at the focal volume. The glass samples were translated along the laser beam direction; therefore elongated optical modifications were formed. Whether the written lines were able to guide light was verified by measuring the near-field profile of the output mode of the waveguide at 660 nm. This way, optical guiding was demonstrated for the sample 25MgO 25ZnO 50P2O5 (mole %). Either tracks of damage or negative refractive index changes did not allow demonstrating guiding for other compositions. The laser-induced structural changes within the glass network were studied by means of spatially resolved micro Raman and fluorescence spectroscopy. While slight or no peak shifts, of relevant Raman bands, were found, a strong fluorescence signal was measured and associated with POHC electronic defect formation. These results and corresponding changes of optical properties are discussed in relation with the O/P atomic ratios favorable for waveguide fabrication.

  8. Electrofluidics fabricated by space-selective metallization in glass microfluidic structures using femtosecond laser direct writing.

    PubMed

    Xu, Jian; Wu, Dong; Hanada, Yasutaka; Chen, Chi; Wu, Sizhu; Cheng, Ya; Sugioka, Koji; Midorikawa, Katsumi

    2013-12-01

    Space-selective metallization of the inside of glass microfluidic structures using femtosecond laser direct-write ablation followed by electroless plating is demonstrated. Femtosecond laser direct writing followed by thermal treatment and successive chemical etching allows us to fabricate three-dimensional microfluidic structures inside photosensitive glass. Then, femtosecond laser ablation followed by electroless metal plating enables flexible deposition of patterned metal films on desired locations of not only the top and bottom walls but also the sidewalls of fabricated microfluidic structures. A volume writing scheme for femtosecond laser irradiation inducing homogeneous ablation on the sidewalls of microfluidic structures is proposed for sidewall metallization. The developed technique is used to fabricate electrofluidics in which microelectric components are integrated into glass microchannels. The fabricated electrofluidics are applied to control the temperature of liquid samples in the microchannels for the enhancement of chemical reactions and to manipulate the movement of biological samples in the microscale space. PMID:24104603

  9. Intermediate band properties of femtosecond-laser hyperdoped silicon

    NASA Astrophysics Data System (ADS)

    Sher, Meng-Ju

    This thesis explores using femtosecond-laser pulses to hyperdope silicon with chalcogen dopants at concentrations above the maximum equilibrium solubility. Hyperdoped silicon is promising for improving efficiencies of solar cells: the material exhibits broad-band light absorption to wavelengths deep below the corresponding bandgap energy of silicon. The high concentration of dopants forms an intermediate band (IB), instead of discrete energy levels, and the IB enables sub-bandgap light absorption. This thesis is divided into two primary studies: the dopant incorporation and the IB properties. First, we study dopant incorporation with a gas-phase dopant precursor (SF6) using secondary ion mass spectrometry. By varying the pressure of SF6, we find that the surface adsorbed molecules are the dominant source of the dopant. Furthermore, we show the hyperdoped layer is single crystalline. The results demonstrate that the dopant incorporation depth, concentration, and crystallinity are controlled respectively by the number of laser pulses, pressure of the dopant precursor, and laser fluence. Second, we study the IB properties of hyperdoped silicon using optical and electronic measurements. We use Fourier transform infrared spectroscopy to study light absorption. The absorption extends to wavelengths as far as 6 mum before thermal annealing and we find the upper bound of the IB location at 0.2 eV below the conduction band edge. For electronic measurements, we anneal the samples to form a diode between the hyperdoped layer and the substrate, allowing us to probe the IB using temperature-dependent electronic transport measurements. The measurement data indicate that these samples form a localized IB at concentrations below the insulator-to-metal transition. Using a two-band model, we obtain the location of the localized IB at >0.07 eV below the conduction band edge. After femtosecond-laser hyperdoping, annealing is necessary to reduce the laser-induced defects; however

  10. Filamentation of Beam-Shaped Femtosecond Laser Pulses

    SciTech Connect

    Polynkin, Pavel; Kolesik, Miroslav; Moloney, Jerome

    2010-10-08

    When ultra-intense and ultra-short optical pulses propagate in transparent dielectrics, the dynamic balance between multiple linear and nonlinear effects results in the generation of laser filaments. These peculiar objects have numerous interesting properties and can be potentially used in a variety of applications from remote sensing to the optical pulse compression down to few optical cycles to guiding lightning discharges away from sensitive sites. Materializing this practical potential is not straightforward owing to the complexity of the physical picture of filamentation. In this paper, we discuss recent experiments on using beam shaping as a means of control over the filament formation and dynamics. Two particular beam shapes that we have investigated so far are Bessel and Airy beams. The diffraction-free propagation of femtosecond Bessel beams allows for the creation of extended plasma channels in air. These extended filaments can be used for the generation of energetic optical pulses with the duration in the few-cycle range. In the case of filamentation of femtosecond Airy beams, the self-bending property of these beams allows for the creation of curved filaments. This is a new regime of the intense laser-pulse propagation in which the linear self-bending property of the beam competes against the nonlinear self-channeling. The bent filaments generated by ultra-intense Airy beams emit forward-propagating broadband radiation. Analysis of the spatial and spectral distribution of this emission provides for a valuable tool for analyzing the evolution of the ultra-intense optical pulse along the optical path.